Streaky Detroit can spread the ball, but woeful in third-down defense [Scouting the Lions]

About this time last year, the Vikings went to Detroit and beat up on Matthew Stafford, sacking him seven times in a 28-19 victory and setting in motion the firing of his offensive coordinator, Joe Lombardi, and both line coaches, Jeremiah Washburn and Terry Heffernan.

The Lions were 1-6 during that confusing period in which coach Jim Caldwell announced there would be no major changes right before changing his mind or being told by da bosses to change it quickly.

Since then, with 32-year-old former quarterbacks coach Jim Bob Cooter as offensive coordinator, the Lions are 10-8, including 4-4 this season.

This time around, it's the Vikings who are unsettled at offensive coordinator after Norv Turner shocked the organization by announcing his resignation on Wednesday morning. In steps Pat Shurmur, who inherits a better record (5-2) than Cooter did last season, but probably not a better situation considering the injury-riddled state of the Vikings' offensive line.

Overview: The Lions have have a perfectly symmetrical stretch of inconsistency this season. They opened with a win, lost three straight, won three straight and then lost at Houston 20-13 last week. They're 3-1 at home, but 1-3 on the road. They scored 39 points in winning their opener at Indianapolis, but have been held under 15 points in two of three road games. Like the Vikings, they lost at Chicago (17-14). Unlike the Vikings, they got to play Philadelphia at home. And that 24-23 victory over the Eagles is their signature win to date. A win at U.S. Bank Stadium on Sunday would change that. The Vikings won both meetings last season, but the teams have split six meetings since 2013. Mike Zimmer is 2-2 against Detroit.

To the tape: …

Top 5 thoughts while watching the Lions' 20-13 loss at Houston:

—That unbridled arm strength is sometimes tough to corral. Although Stafford's touch has improved over his 101-game career, it's not always there. And that could be a reason the Lions went into last week's game leading the league with 16 drops. There were drops on back-to-back plays in the first quarter.

—I've never seen running back Theo Riddick look so quick, so fast, so fresh and, well, so good. A poor man's Reggie Bush in that 5-9, 201-pound frame. After missing the previous two games with an ankle injury, he blasted out of the gates early on against the Texans. He didn't have a huge game, but he proved he's a concern as a runner and receiver. With 56 yards rushing and 77 receiving, Riddick had a career-high 133 yards from scrimmage. He also had his fourth receiving touchdown of the season.

—General Manager Bob Quinn spent the past 16 seasons in New England's front office before joining the Lions this season. He arrived with a clear priority to upgrade the offense. He landed the top receiver in free agency, Marvin Jones, and spent two of his top three draft picks on offensive linemen. His first pick, left tackle Taylor Decker, and third-round pick, left guard Graham Glasgow, are starting. Decker has started all eight games, while Glasgow will be making his fourth straight start on Sunday.

—I was impressed by Stafford's protection. He was sacked only one time on the road at Houston. Vikings right tackle T.J. Clemmings gave up twice that in a home game against the Texans. But, in fairness to the Vikings, it helps that Detroit has had both of its starting tackles for all eight games.

—This team missed cornerback Darius Slay (hamstring) last week. He was limited in practice on Wednesday, but the fact he practiced at all is an indication he could be ready to play. Having said that, his replacement, fifth-year journeyman Johnson Bademosi, did jump a route and intercept a pass that led to a field goal right before half last week.

—Good news for Kyle Rudolph, who caught touchdown passes in both wins over the Lions last season: This team can't cover tight ends. From the Houston tape, it's clear that's a struggle for the Lions because they don't have a linebacker or a safety who's up to the challenge. Ten of Houston's 20 completions went to tight ends. Early on, the completions were back-breakers for a Lions defense that ranks last in the league in allowing third-down conversions (49.5). On the 61-yard touchdown drive that gave Houston a 7-0 lead, tight ends accounted for 40 yards, including a 23-yard catch on third-and-8, a 12-yard catch on third-and-10 and a touchdown on third-and-goal from the 6.

Key stat: 49.5.