EAGAN, Minn. -- The Minnesota Vikings fired defensive coordinator Ed Donatell on Thursday, an unsurprising decision even after winning 13 games under first-year coach Kevin O'Connell.

The team did not immediately name a replacement. In a statement, O'Connell said in part: "We will immediately begin our search to fill this critical role as we continue to build a championship standard for the Minnesota Vikings."

Although they won the second-most regular season games in team history, the Vikings' defense was one of the worst in franchise history. It finished the season ranked No. 28 in points allowed (25.1) and No. 31 in yards allowed (388.7). On Sunday, the New York Giants gashed the Vikings for 31 points and 431 yards, including five scoring drives of at least 75 yards and a total of 18 plays that gained 10 or more yards.

Donatell's future had been in question since Week 14, when O'Connell said publicly that he was considering all options to improve the defense other than changing schemes entirely. When asked if he would make staff changes, or tap a new defensive playcaller, O'Connell said he wasn't considering that option "as of right now."

O'Connell hired Donatell in part for his connection to the 3-4 scheme popularized by longtime NFL defensive coach Vic Fangio, most recently the Denver Broncos' coach from 2019-21. Donatell served as Fangio's defensive coordinator in Denver and also coached with him at previous stops with the Chicago Bears and San Francisco 49ers.

O'Connell outlined his thought process shortly after hiring Donatell, saying: "What do you not like to play against? What's the hardest defensive scheme to play against? What keeps you up at night as you game plan?"

But Donatell's version of the scheme quickly proved to be predictable and often ineffective. It drew national scrutiny as early as Week 2, when ESPN analyst Troy Aikman called out the soft zone coverage the Vikings used as the Philadelphia Eagles moved the ball up and down the field in a 24-7 loss.

Donatell made clear that his core philosophy was to rely on his front four -- especially linebackers Za'Darius Smith and Danielle Hunter -- to apply enough pressure to allow the rest of the defense to sit back in zone coverage. But the Vikings' four-man rush managed a 23.9% pressure rate during the regular season, the ninth lowest in the league, and their shell zone left far too much room for easy yards.

After the defense allowed more than 400 yards for the fifth consecutive game last month against the Detroit Lions, O'Connell directed Donatell publicly and privately to make changes. Donatell did make some tweaks to their pass rush schemes, personnel usage and coverage types, but it did not lead to significant improvement.

Overall, the Vikings were in their nickel personnel group on 80.4% of snaps, the third-highest rate in the NFL, according to NFL Next Gen Stats. They were in split safeties on 50.4% of their defensive snaps, the league's fifth-highest rate. They used zone coverage at a rate of 79.4%, the fourth highest in the league, and they blitzed at the NFL's 12th-lowest rate (22.1%).