Over the next two weeks, we will take a position-by-position look at where the Vikings stand heading into the offseason after their 7-9 season in 2014. Today, we break down the defensive line.

One of the first acts of business of the Mike Zimmer era was overhauling the defensive line. The Vikings let defensive tackle Kevin Williams and defensive end Jared Allen walk in free agency, they added nose tackle Linval Joseph in free agency and they re-signed defensive end Everson Griffen to a big contract.

When the season started, the Vikings had three new starters on the defensive line and five of the eight players in their rotation were in their first season in Minnesota. The defensive line would turn out to be the deepest and arguably the most valuable position group on the roster.

In his first season as a starter, Griffen finished ninth in the NFL with a dozen sacks while also defending the run well. Second-year defensive tackle Sharrif Floyd took a giant leap forward under Zimmer with 4.5 sacks and five other tackles for a loss. Journeyman defensive tackle Tom Johnson surprised with 6.5 sacks as a reserve. And the Vikings finished ninth in the NFL with 41 total.

But it wasn't all roses along the defensive line. Joseph was merely average, and veteran end Brian Robison had a down season. The pass rush disappeared at times when individuals freelanced and the Vikings as a team struggled to stop the run, finishing 2014 ranked 25th in run defense.

Still, the defensive line was a strength and with a little tweaking it should continue to be in 2015.

ONE REASON FOR OPTIMISM: While injuries limited Floyd to 14 games and 568 total defensive snaps, he made a major impact whenever he was on the field and unhampered by injury. Floyd finished with 30 total pressures, according to Pro Football Focus, which tied for 13th in the NFL. And he often stormed into the backfield to blow up running plays. Floyd had big shoes to fill in replacing Williams, a six-time Pro Bowler with the Vikings, but Floyd came through, showing the kind of ability that made the team so excited he fell into their laps during the 2013 draft.

ONE REASON FOR CONCERN: Robison has been an underrated player for years (I remember that when I covered the Ravens in 2013, they were just as concerned about him as Allen). But his 4.5 sacks were his lowest in his four years as a starter and he wasn't particularly stout against the run. Now, Zimmer was quick to point out after the season that Robison was asked to do some things differently this season, and his dirty work might not have shown up on the score sheet. But Robison turns 32 in April, and if his play doesn't pick up in 2015, it could be his last season with the Vikings.

GRADES WITH A GRAIN OF SALT: Since the Vikings (understandably) won't make their player grades public, we turn to Pro Football Focus, whom some players and coaches have been critical of. For context with these grades, a grade of 0.0 is considered average. Positive grades are good. Negative grades are not. Floyd, the league's fifth-best defensive tackle according to PFF, led the group with a plus-22.0 grade. Griffen was a plus-16.8. Johnson was a plus-5.2 for his work as a sub pass rusher. And Joseph was a plus-1.3. Corey Wootton, a reserve defensive end, had the lowest grade at negative-14.8. Robison was a negative-12.2. And rookie nose tackle Shamar Stephen graded out as a negative-8.0, though it's worth noting that the coaching staff was pleased with how Stephen played while shuffling between both tackle spots.

STAT THAT STANDS OUT: 64 — total pressures for Griffen, tied for fifth among 4-3 defensive ends.

POTENTIAL DEPARTURES: Johnson and Wootton are both free agents. The Vikings will likely let Wootton, who disappointed with just one sack, walk. But bringing back Johnson would make a lot of sense for both parties if they can find financial common ground. Johnson has said he wants a two-year contract, and one would think the Vikings can make that happen for the valuable backup. And Johnson should remember that he had more sacks this season playing for Zimmer and defensive line coach Andre Patterson than he had in his entire career before coming to Minnesota. As for potential cuts, it wouldn't be a surprise if the Vikings approached Robison about reducing his $5.45 million cap number. But it would be a surprise if he did not return for 2015.

OFFSEASON LEVEL OF NEED: Low. The Vikings have much more pressing needs than their defensive line, which should remain mostly intact for the upcoming season. If they cannot re-sign Johnson, that would leave a void, though I'm sure Zimmer and the coaching staff feel they could coax that kind of production out of someone else. The team could look to improve the depth at defensive end. Scott Crichton, picked as a potential replacement for Robison down the road, hardly saw the field as a rookie, though it's too early to count him out. And Crichton isn't exactly a speed rusher, and the Vikings would like to have another one of those to back up Griffen.