EAGAN, Minn. — The Vikings have a lot of decisions to make this offseason.

One of the more pertinent areas Head Coach Kevin O'Connell and General Manager Kwesi Adofo-Mensah will be evaluating throughout the coming weeks is trying to improve a defense that finished 31st in yards allowed and 30th in points against in the regular season.

When O'Connell and Adofo-Mensah addressed Twin Cities reporters in Wednesday's end-of-season press conference, they were asked about defensive struggles.

O'Connell said the team is in "evaluation mode of everything that we did."

"My job throughout the year was trying to find ways to help and improve and what it was going to take to win each individual game and some of those close games and some of the turnovers for us and some of the plays that were made on that side of the ball," O'Connell said. "We know, statistically, that standard we fell below what we had hoped to be, both schematically and in our performance on the field.

"I think it's very important we look at from a standpoint of the why. Why did it happen? What were the contributing factors that were both in our control and out of our control?" O'Connell continued. "And make sure we're facing that head-on, from an accountability standpoint and ultimately doing whatever we need to do to make sure we're able to show some improvement in that area and see if we can play the ultimate goal of that complete complementary football that is very important to winning consistently in this league."

When asked if Defensive Coordinator Ed Donatell would return for a second season, O'Connell said evaluations were an "ongoing process."

"I think that's really important – part of self-reflecting and part of us reflecting as a staff – is making sure we're looking at every aspect of our football team and our coaching staff to make sure we're doing everything within my responsibility and my power to put our players and our organization in the best possible situation to have success," O'Connell said. "So that is an ongoing process that is continuing as we speak, and we'll continue throughout the rest of this week. I think it's important to do, and I think after the success we had this year and then coming up short of where we ultimately wanted to get to, I think it's the right thing to do – to make sure I go through that thorough process in doing so."

Under Donatell, the Vikings implemented a 3-4 base defensive scheme for the first time since 1985. There were bright spots, such as getting crucial takeaways down the stretch of games that helped Minnesota win an NFL-record 11 one-score games. But the Vikings defense struggled on multiple occasions, allowing 400-plus yards to opponents in 10 of their 18 games this season, including a stretch of five consecutive games.

O'Connell said it will be a "mix of both" as he and Adofo-Mensah evaluate the team's defensive scheme and its personnel.

"Knowing that I'm responsible for whatever schemes we put on the field, that evaluation process goes through not only the course of this season and my role in contributing to the three phases of our team but also throughout the year. The expectations that were in place and the hopes and goals for our team tied hand in hand, week in and week out, [of] 'What's it going to take to win a football game?' " O'Connell said. "And the ebbs and flows of a season, I think when you look back through it, scheme-wise, there's always going to be things I know offensively we can do differently, better for our players. Special teams feels the same way. Defensively, it's the same thing with that evaluation process, understanding what we were this year, the reality of it, being accountable to that and then understanding in my role and responsibilities, fixing the problems and making sure whatever path we take moving forward is in the best interest of continuing on a track to be at that championship standard."

O'Connell added there were some layers to the team shifting to a 3-4 from a 4-3 in previous seasons defensively and said the coaches must make sure the players are making a seamless transition into new roles.

"I think first and foremost, you've got to really understand what that transition really looked like from the standpoint of what snaps are we really talking about from a 3-4 to a 4-3," O'Connell said. "You look at the true percentages of time that true base defense was in the game, on the field and understanding what that percentage looks like compared to when you are in your 4-2 nickel front and everybody is really just in a nickel variation of a 4-3 defense, so every team in this league goes through the roster-evaluation process of trying to fit players to the roles that you believe are best for them.

"I feel like some of our guys really handled that with ease. Some of our guys, it was a work in progress, really finding their premier role and how they can thrive, and ultimately, that's on us as coaches and me as the head football coach to make sure I look long and hard at that and then decide what's the best thing for our team moving forward, both from a personnel standpoint of working alongside Kwesi and how we deploy our personnel," O'Connell continued. "Those schemes that you're talking about, that's what we're doing right now, really looking at that 25 to 28, whatever the true percentage of true base 3-4 that was on the field and deciding in comparison to the rest of those snaps how we used our players and could have been better for them and how we make sure we rectify the areas where we weren't good enough."

O'Connell said opposing teams are continuing to take advantage of open space through manipulating formations and the use of pre-snap motions, so every team is trying to add more speed on its roster. That can be particularly true for a team that plays home games indoors and on a turf surface instead of outdoors and on grass.

"I think you're just seeing the ball find its way into space a little bit more. You see some of the best plays, the biggest plays in our league from this year and you go back and study what that is, and it's a lot of individual players making momentous plays in those moments where they have the ball in their hand in space," O'Connell said. "I think it's an important thing and I think speed on your roster is something that can stand the test of a season, shows up time and time again, and I think it's an important thing that all 32 teams are constantly looking to add and use and do it in the ways that fit their particular schemes is one thing, but then how it just affects and changes the other team's ability to try to stop what you're doing."