The Vikings defense became the NFL's first since the Tampa Bay Buccaneers of the 1998 and 1999 seasons to force the fewest passing touchdowns in back-to-back seasons.

Historical success wasn't uninterrupted. Early hiccups and an infusion of young talent for ailing starters led to the ninth-most explosive pass plays allowed (10 of 40-plus yards), tied for the Vikings' worst mark in the Mike Zimmer era.

Grades are based on a 1-to-5 scale, with '5' marking excellence, '4' for above-average, '3' for average, '2' for below-average and '1' for failure to perform. Players that did not accrue a season (weren't on the active roster for at least six weeks) or played in three games or fewer are not graded. Below are individual grades, based on game and practice observations, weekly film reviews and interviews with coaches, for 13 defensive backs who finished the season on the Vikings' active roster, injured reserve or practice squad. Unofficial NFL stats, such as QB pressures, missed tackles and targeted passes, are compiled by

Previously: (Linebackers) Anthony Barr's contract season leaves you wanting more; (Defensive linemen) Danielle Hunter's name now among the NFL's best

S Harrison Smith (4.5) — A safety disruptive near and far from offenses, Smith was again the Vikings' Swiss Army Knife in 2018. Led all defenders with 1,024 snaps [98.6%]. One of five Vikings to play more than 1,000 snaps. Named to a fourth straight Pro Bowl. Six All-Pro votes led the team. Just one of three NFL defensive backs with three interceptions and three sacks, joining the Chargers' Derwin James and Atlanta's Brian Poole. The primary blitzer in the secondary, Smith forced nine pressures (three sacks) during 39 rushes. Masterful at disguising and timing his pass rush at the snap. Baited Josh Rosen into an interception to Anthony Harris in the Week 6 win vs. Arizona by faking a blitz to one side, then bailing into deep coverage with Harris rolling underneath to the other side. to the Vikings' run defense. Smith started playing more of a linebacker role in Weeks 8-11 when Anthony Barr was injured. Only four safeties had more run stops (18) than Smith; none had fewer missed tackles (one). Coaches rave about Smith's preparation, vision and closing speed leading to anticipatory plays behind the line of scrimmage. Had a season-high four stops in the Week 16 win at Detroit, including two for a loss. Remains a hard hitter, jarring the ball loose from Alshon Jeffery on a deep third-and-20 pass in the fourth quarter at Philadelphia. Penalized once (and fined $10,026) for the late hit that injured Bears quarterback Mitchell Trubisky's shoulder. one touchdown in coverage when San Francisco's Dante Pettis turned upfield on him during a scramble drill for a 22-yard score in Week 1. Ended the same Sunday with the game-sealing interception off Jimmy Garoppolo. Put in man-to-man and zone coverage situations. He's credited by teammates for on-field communication on upcoming plays and adjustments. Gambles didn't always pay off. Got beat on 35-yard and 40-yard catches against Arizona. Messed around before the snap and got beat on a 22-yard throw to Kevin White in the season finale loss to the Bears. Set to have the seventh-highest cap hit ($10.75 million) among NFL safeties next season, which is a relative bargain for the Vikings.

More reading: Boxing, flying and Big Brothers Big Sisters – How Harrison Smith keeps a measured approach to his craft.

S Anthony Harris (4.0) — Harris took control of the starting job Week 8 against the Saints and didn't let go. The former undrafted safety started the final nine games in a breakout season. Played 623 snaps [60%]. Tied for the team lead with three interceptions, including two off Mitchell Trubisky in the Week 11 loss at Chicago. Jumped a Larry Fitzgerald route for an interception in the win against Arizona. Broke up a goal-line Tom Brady pass to Julian Edelman in the loss at New England. Regarded as a film junkie who gets razzed in team meetings for knowing it all. So it's little surprise he's earned Mike Zimmer's trust as the starting safety. Rarely caught out of position. Isn't the most athletically gifted player, but makes up for it with everything else. Not flagged. Missed two tackles, including Jordan Howard on a 42-yard run in the season finale loss. Pending restricted free agent.

More reading: 'That's too easy for him.' Anthony Harris keeps Vikings teammates on their toes in meeting rooms.

CB Trae Waynes (3.5) — Waynes went from one of the NFL's most targeted cornerbacks in 2017 to one of the least targeted this season. The credit starts with his coverage. Played 692 snaps [66.6%]. Allowed 36 catches on 54 targets for 429 yards, two touchdowns and an interception. Missed two starts due to concussions. Also left games against the 49ers, Bills, Rams, Jets and Patriots due to injuries. Returned in New York after a few plays and had his best game, deflecting three Sam Darnold passes and grabbing an interception. Beat on a ridiculous Jared Goff throw for a 47-yard touchdown in Los Angeles. Did not play in the second half due to a concussion. A sure and willing tackler and run defender who surrendered just 90 yards after the catch, fifth fewest among all NFL corners. Ranked ninth with eight run stops — second in the Vikings secondary. Penalized three times, twice for pass interference. Missed three tackles. Could stand to make more plays on the ball. Waynes had a solid season, though durability is a concern. The Vikings front office has a decision to make with his $9.069 million option for next season not guaranteed until March.

CB Mackensie Alexander (3.5) — Eventually made a leap in his third NFL season, Alexander became the Vikings' steady slot cornerback after rotating with others throughout the first half of the season. Played 564 snaps [54.3%]. Missed the season opener due to an ankle injury suffered in an exhibition against the Jaguars. Played through a knee injury in New England, where he was pulled from the game after allowing a couple of big completions on the first drive. Settled into the disruptive pass defender the Vikings' brain trust saw when drafting him in 2016's second round. Eight of his team-leading 10 pass deflections came after Nov. 18. Showed his range in that Chicago game. Deflected two fourth-quarter Trubisky passes; the first was a Tarik Cohen screen he quickly identified and the second came in slot man-to-man coverage on Allen Robinson. Made critical third-down deflections in man coverage against the Cardinals and Dolphins. Had the most sacks (4) by a Vikings defensive back since Robert Griffith in 1999. That was a product of blitz design, disguise and setup. Alexander was literally not touched on all four sacks. Still has work to do as a tackler, missing seven. Flagged six times (three declined). Put together the kind of season that builds confidence for the future. Entering a contract year in 2019.

More reading: The game is becoming fun again for Mackensie Alexander.

CB Xavier Rhodes (3.0) — From start to finish, Rhodes was questionable to play for the Vikings in his sixth NFL season. Ready? (*inhales deeply*) A hamstring injury had him listed questionable in Weeks 1 and 13. A foot injury had his availability in doubt in Weeks 8 and 9. He missed the Saints game. Then a groin injury prevented him from playing in the season finale loss to the Bears. Played 769 snaps [74%]. Coming off an All-Pro season, Rhodes said injuries disrupted his ability to play well when he was on the field. Started out well shadowing Marquise Goodwin before the 49ers receiver's injury. Then allowed nine catches for 70 yards and a touchdown in Green Bay. Had trouble with Davante Adams this season, also called for a 26-yard interference penalty and allowed a 15-yard touchdown on the same drive of the Week 12 win. Held Rams star Brandin Cooks to one catch for nine yards before the third quarter, when he was pulled by Mike Zimmer after kicking a penalty flag and drawing unsportsmanlike conduct in reaction to being called for holding. Cooks caught a 47-yard touchdown on the next play of the Week 4 loss. Fined $13,369 for kicking the flag. Lost out on $62,500 from two missed games due to per-game roster bonuses in his contract. Led the team with nine penalties (three declined), six for some form of illegal contact.

Still one of the league's most disruptive man-to-man corners when healthy and concentrated. Held Alshon Jeffery to two catches for 39 yards in the Week 5 win at Philadelphia, getting beat on a fourth down. Tipped a Sam Darnold pass into a Harrison Smith interception during the Week 7 win at New York. Played well against Allen Robinson in Chicago, where the Bears star had three catches for 39 yards. Had a career-low seven pass deflections on the season. His lone interception was an overthrown Jimmy Garoppolo pass on a slant route in Week 1. Ranked 29th in yards (470) and 35th in QB rating (88.4) allowed. An inconsistent and injury-plagued season. Missed three tackles.

More reading: Xavier Rhodes says 'lesson learned' about returning too quickly from injuries.

CB Holton Hill (3.0) — A coveted undrafted signing, Hill received more guaranteed money ($75,000) than any undrafted addition in the Mike Zimmer era. The former Texas corner arrived in Eagan as an athletic project and emerged from his rookie season with 374 snaps [36%] under his belt. Started three games, all in big spots against the Saints, Seahawks and Bears. Had three deflections in Seattle, but also missed two tackles. Made the smart play on a first-down deep shot by Russell Wilson, turning for the ball to avoid pass interference and nearly intercepting him. Not the quickest to identify running plays. Ended on a down note against the Bears in the season finale. Beat by Taylor Gabriel on a 40-yard deep ball to set up a one-yard touchdown run. Also bounced off Jordan Howard to allow a six-yard touchdown run. Played 260 special teams snaps [58.2%]. Penalized twice, including a 20-yard interference penalty on a Patriots touchdown drive. Another promising young cornerback in the mix with plenty to polish.

CB Mike Hughes (2.5) — Drafted 30th overall out of UCF, Hughes surprised Vikings coaches with his initial grasp of a complicated position at 21 years old. Hyper-quick feet helped him earn playing time right away as a slot defender and primary backup on the outside. Played 243 defensive snaps [23.4%] before tearing his ACL in Week 6 against Arizona. Returned a Jimmy Garoppolo interception 28 yards for a touchdown in his first game. Still made rookie mistakes in coverage. Appeared to be the culprit for busted coverage on Kyle Juszczyk's 56-yard catch and run in Week 1. Got caught in a miscommunication with Eric Kendricks leading to a 26-yard touchdown in the Week 3 loss to Buffalo. Lost the ball on a 48-yard toss to Shelton Gibson in Philadelphia. Returned four kickoffs for a 26.7-yard average. Not flagged. Missed four tackles in coverage. Showed plenty of reason for excitement. Athletically gifted enough to stick with speedy receivers in coverage. Flashed traits as a hard-nosed slot and outside defender, unafraid to tackle in heavy traffic. Forced a Brandin Cooks fumble in the fourth quarter. The Vikings may have found a gem if he can pick up where he left off.

DB Jayron Kearse (2.5) — Appeared in all 16 games, mostly as a specialist, during his third NFL season. Earned a role as a slot defender in a 'big nickel' package and played 202 snaps [19.4%] on defense. Long arms allow Kearse to make plays when in position, like his third-down deflection in the end zone against the Rams' Cooper Kupp. Grew into a strong downhill defender with 11 stops (six vs. pass, five vs. run) without a missed tackle. Room to improve in coverage after allowing 13 catches on 16 targets for 89 yards, including a 17-yard catch near the goal line to set up a Jets touchdown. Penalized four times (one declined); his defensive holding in the season finale negated an Anthony Barr sack on Mitchell Trubisky. A strong gunner on special teams. Played 241 snaps [53.9%] there. Entering a contract year in 2019.

S Andrew Sendejo (2.0) — One of the Vikings' undrafted-to-starter stories, Sendejo could have played his last snap for Minnesota. Landed on injured reserve after Week 5 because of a groin injury. Played 324 snaps [31.2%] after missing time in the spring due to a back injury. His highlight was ripping loose a touchdown catch from Charles Clay in the Week 3 loss to the Bills for the season's lone pass deflection. Had as many missed tackles (4) as stops (4). Penalized twice for unnecessary roughness. Fined $53,482 as a repeat offender for hitting Packers receiver Davante Adams. A disappointing and injury plagued contract season for Sendejo, who has an expensive $5.5 million team option for 2019 that appears unlikely to be picked up by the team. Turns 32 in September.

S George Iloka (2.0) — Signed Aug. 22 in the same month he was a surprise cut by the Bengals. Didn't see action on defense until injuries ended Andrew Sendejo's season. Started three games, but was yanked from the third (Week 8 vs. New Orleans) after a 44-yard trick play from Taysom Hill to Michael Thomas over him on the fifth snap. Played 116 defensive snaps [11.2%]. Forced a fumble on Jets returner Andre Roberts that went out of bounds. Played 238 special teams snaps [53.2%]. Didn't get many opportunities in Minnesota and is unlikely to return. Pending free agent.

CB Marcus Sherels (2.0) — Again evaded competition to remain as the Vikings punt returner in his ninth NFL season. Ranked sixth with 12 yards per return, including a 70-yard sprint against the Dolphins. Sherels, 31, took heat from teammates on the sideline and after the game for being caught 22 yards shy of the end zone. Missed four games due to rib and foot injuries. Played 190 special teams snaps [42.5%]. Named a second Pro Bowl alternate as a specialist. Did not fumble for the third season as punt returner. Played 29 defensive snaps [2.8%], allowing a 24-yard catch by Josh Gordon. Pending free agent.

CB Craig James (N/A) — The undrafted rookie was cut after the preseason and re-signed to the practice squad in October. Promoted to the active roster Week 13 for depth. Played 25 special teams snaps in three games.

CB Jalen Myrick (N/A) — Signed Sept. 5 to the practice squad after roster cuts. The ex-Gophers defender and return man was re-signed in October and was one of 10 practice squad players to sign a futures deal Jan. 2.