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 will focus on the offensive line.

The Vikings figured that their offensive line would be a strength in 2014. After all, all five of their starting linemen were back for a third straight season and they figured they had one of the league's better offensive tackle combos in former Pro Bowler Matt Kalil and big Phil Loadholt.

But offensive line play ended up being one of the team's biggest weaknesses due to the struggles of Kalil and other starters, along with a bunch of injuries along the offensive line.

Right guard Brandon Fusco, who was rewarded with a contract extension before the season opener then was lost to a torn pectoral muscle two weeks later, was the first starter to go down. In Week 12, Loadholt, their right tackle, suffered a similar season-ending injury. Left guard Charlie Johnson, who struggled mightily in 2014, missed two games late in the season before returning for the finale.

Those injuries forced backup linemen Joe Berger, Mike Harris and Vlad Ducasse into action.

The offensive line played better late in the season, but the Vikings allowed 51 sacks on the season, the fifth-highest total in the league. Kalil was responsible for 12 of them, per Pro Football Focus.

ONE REASON FOR OPTIMISM: Silver linings are a little harder to spot at this position group, but veteran center John Sullivan was solid in 2014 despite all of the moving parts around him and Fusco, who was becoming one of the league's better right guards, will be back healthy in 2015.

ONE REASON FOR CONCERN: There are reasons for concern at left guard (they need to find one) and right tackle (Loadholt's pectoral injury could sideline him until training camp), but they pale in comparison to what is up with Kalil. As a rookie, Kalil, the fourth overall pick in 2012, made the Pro Bowl and looked like a long-term answer at left tackle. He did not play as well in 2013, and after missing workouts this past spring due to offseason knee surgery, Kalil's performance plummeted. He was one of the league's worst tackles in pass protection and admittedly endured lapses in confidence. This spring, the Vikings must decide whether to pick up his fifth-year option to secure his services through 2016. It seemed like a no-brainer before the season, but now it will require careful consideration.

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. Sullivan, Berger, Fusco and Loadholt (barely) all earned positive marks, and Sullivan's plus-5.6 grade was the highest among all Vikings offensive players. But only three NFL offensive tackles graded out worse than Kalil, who was a negative-29.1. Ducasse and Johnson also graded poorly at negative-14.1 and negative-12.1, respectively.

STAT THAT STANDS OUT: 55 — total pressures allowed by Kalil this past season, per Pro Football Focus. Only Dolphins rookie right tackle Ja'Wuan James surrendered more than Kalil, who gave up 12 sacks, seven other quarterback hits and 36 hurries in 16 games.

POTENTIAL DEPARTURES: Johnson is expected to be released, leaving an opening at left guard. Berger, Harris and Ducasse are all scheduled to become free agents. Bringing back Berger, who was solid as a replacement at center and guard, makes sense for both parties. Harris, who just turned 26, is a tougher call. And the Vikings can do better than Ducasse, who will likely be allowed to walk.

OFFSEASON LEVEL OF NEED: High. General Manager Rick Spielman recently said that the team has identified eight positions that need to be improved, and left guard has to be at or near the top of the list. Kalil's struggles were compounded by the play of Johnson, and the Vikings will look to upgrade at left guard through free agency or the draft. They must also figure out what to do at the left tackle position. Kalil isn't going anywhere, and the team will give him every opportunity to be the starter again in 2015. But it would be wise to add a reliable backup plan at his position, whether it is signing a veteran with starting experience or drafting another left tackle prospect. And with three backups becoming free agents, the Vikings will have to restock the bottom of their depth chart.