MINNEAPOLIS — The Minnesota Vikings, still seeking to salvage a season that started with Super Bowl designs, made a last-ditch move to capture a mid-December spark by firing offensive coordinator John DeFilippo.

Coach Mike Zimmer made what he called an “extremely difficult decision” on Tuesday morning, following a 21-7 defeat at Seattle on Monday night . DeFilippo’s first season on the job ended after just 13 games, amid a sharp decline in production by the offense over the past six weeks.

“I went round and round and round and round about it because I feel like, ‘I hired him. It’s my job to try to help him to continue to get better,’” Zimmer said. “I obviously didn’t do a good enough job there. I’ve always felt like if you hire a guy, you should stick with him and try to help him and help him mature as a coach.”

The Vikings (6-6-1) have been held to under 300 total yards in four of their past five games. They’ve scored an average of 12.8 points in those four games. Thanks to the struggles of several of their NFC competitors, though, they’re still in control of the second wild-card spot with three games to go.

“I don’t want the season to be wasted. Now, maybe it will. Maybe it won’t,” Zimmer said. “But these three games, to me, are very, very critical.”

Quarterbacks coach Kevin Stefanski was made interim offensive coordinator, taking over the play-calling duty. Stefanski has been an assistant with the Vikings since 2006, surviving two head coaching changes. Having coached quarterbacks, running backs and tight ends under Zimmer, Stefanski has a firm grasp of the scheme and the personnel.

“We’ve got a lot of smart guys in that room, and I’ll try to help him best I can,” Zimmer said.

DeFilippo’s work with new quarterback Kirk Cousins didn’t materialize into consistent success, but Zimmer said his reasoning for dismissing DeFilippo transcended Cousins and his so-so first year with the Vikings.

“This really wasn’t about one guy. This was about a lot of us holding up our end of the bargain. It was a collective thing,” Zimmer said on a conference call with reporters. He added: “We had to shake things up and try to get better.”

Stefanski will be the fourth play-caller in five years under Zimmer, whose first offensive coordinator, Norv Turner, resigned halfway through the 2016 season. Pat Shurmur thrived in the role last year, behind a career-best season for fill-in quarterback Case Keenum and a 13-3 record that propelled the Vikings to the NFC championship game.

Shurmur, however, was hired as head coach of the New York Giants. He wanted to bring Stefanski with him, but Zimmer blocked that move out of a desire to keep him on his own staff.

The 40-year-old DeFilippo came from Philadelphia, lauded for his work as quarterbacks coach with Carson Wentz and then Super Bowl MVP Nick Foles. He had previously served one season as an offensive coordinator, in 2015 with Cleveland.

The Vikings, who committed a guaranteed $84 million to Cousins on an unprecedented three-year contract, piled up the passing yards over the first eight games. Adam Thielen and Stefon Diggs were dominating opposing teams, and the Vikings topped 400 total yards four times.

Lately, they’ve been unable to generate nearly enough points to stay in the NFC North race with Chicago (9-4). Zimmer publicly questioned DeFilippo’s decision-making more than once over the past month, stressing his interest in more of a run-pass balance and chiding him at one point for essentially trying to trick too many teams rather than relying on the offense’s strengths.

The Vikings didn’t cross midfield on Monday night until late in the third quarter. They actually had a prime opportunity to pull out a victory down the stretch, after a 48-yard pass by Cousins to Diggs set them up in the red zone. They had first-and-goal from the 4, but Cousins threw two incompletions, missing an open Thielen on fourth down and misfiring to tight end Kyle Rudolph instead.

“I think the added piece of the disappointment is when your defense is playing so well,” Cousins said after the Vikings went scoreless against the Seahawks until a garbage-time touchdown with 1:10 left in the game.

He added: “If our offense would bring it the way that we brought it in the earlier weeks of the season, we could be pretty dangerous. Unfortunately, we haven’t put the whole complementary football together enough this season to really be the team that I think we know we’re capable of, and that will be the challenge these last three weeks.”