There have been no doubts about the brand of football the Vikings seek to play, not since Mike Zimmer was introduced as their ninth head coach on Jan. 15, 2014.

Zimmer introduced a mantra that day he has used many times since.

"I want Vikings football to be a tough, smart and aggressive team that plays with passion," he said at his introductory news conference. "I want our fans to be proud of the way we play: tough, resilient, physical football and a team that makes big plays and represents them on the field and in the community."

He is now the third-longest-tenured coach in Vikings history, thanks to teams that have won 56.3% of their regular-season games while hewing largely to the brand.

The Vikings defense jumped from 31st to 11th in points allowed during Zimmer's first season, and ranked in the top 10 for each of the next five years, helping them reach five playoff games despite only being ranked in the top 10 in scoring offense twice (in 2017 and 2019, the years they won playoff games). They set a league record for third-down defense in 2017, led the NFL again in 2018 and weren't among the top half of the NFL in penalties in any season from 2014 to '20.

Days before the Vikings' wild-card playoff game against the Saints in January 2020, co-owner Mark Wilf penned a statement in support of Zimmer amid rumors the coach could be on his way out. The Vikings upset the Saints in overtime that Sunday, allowing them to smirk at critics and clearing the way for Zimmer and General Manager Rick Spielman to get three-year extensions that summer.

They are 10-15 since the Saints victory, having missed the playoffs in 2020 and starting 3-5 this year. As the Vikings head west to face the Chargers on Sunday, badly in need of a win after a tumultuous week, their brand might be in as much jeopardy as ever.

All five of their losses this season have come by seven points or less. They have blown second-half leads in each of their past four games, losing in overtime in Baltimore last Sunday and in the last minute against the Cowboys after pulling out last-minute drives to beat the Lions and set up an overtime win over the Panthers.

The offense has sputtered under first-year play-caller Klint Kubiak, with game-opening scoring drives giving way to confounding stretches where Kirk Cousins doesn't get the ball to Justin Jefferson or Adam Thielen.

The Vikings are tied for 10th in the league in penalties; their 15 offensive holding penalties are tied for second. Against the Cowboys two weeks ago, Zimmer was flagged for calling back-to-back timeouts; on the ensuing play, Ezekiel Elliott ran through tackle attempts from Anthony Barr, Mackensie Alexander and Xavier Woods to convert a third-and-11 that would allow Cooper Rush to win his NFL debut as a starting quarterback.

As chaotic weeks in Zimmer's eight seasons go, this one might not quite reach the level of Week 3 in 2014 (when Adrian Peterson was placed on the commissioner's exempt list after being indicted on child injury charges) or any of several in 2016 (when the Vikings scrambled to trade for Sam Bradford after Teddy Bridgewater's knee injury or offensive coordinator Norv Turner quit after a Halloween night loss to the Bears that also triggered the first of Zimmer's eight eye surgeries).

But the Vikings have placed six players on the COVID-19 reserve list in the past eight days, including safety Harrison Smith hours before the Ravens game and guard Dakota Dozier, who was hospitalized because of the coronavirus Tuesday. Zimmer said Wednesday he was one of 29 people in close contact protocol requiring extra testing. That was in the same news conference he needed to affirm running back Dalvin Cook's playing status after a former girlfriend filed a lawsuit accusing him of assaulting her last November.

The injured list that already included defensive end Danielle Hunter and cornerback Patrick Peterson continued to grow. Barr will miss his fifth game this season because of a long-standing knee issue; nose tackle Michael Pierce will miss his fourth in a row with an elbow injury that landed him on injured reserve Saturday.

If the Vikings can cap this week by winning at Los Angeles, Zimmer could emerge with an opportunity to showcase another key element of his persona: pugnacious, resolute and reveling in the chance to prove people wrong.

"Hey, you know, this team fights, OK?" the coach said Wednesday. "They compete like crazy. We had [89] plays on defense last week, but they fought to the very, very end. ... I've never seen that in my entire career, have that many games come down to the last play of the game. We've got to figure out how not to let it come down to the last play of the game, number one, and when we do, we've got to figure out a way to get it done. I promise you our coaches, and it's my responsibility that it's coming down to the last part of the game, but the players are playing their rear ends off, and we as coaches we're trying to figure out how can we put them in these situations, and unfortunately they're all a little bit different.

"We're trying to work though all of them so we can start winning these games. We haven't won them yet. We've had a little bit of the injuries and COVID and things like that, and we've just got to overcome it. But as long as we keep fighting, good things will happen."

The Vikings need them to happen quickly.

They are tied for ninth in the NFC at 3-5. A victory Sunday would keep them in the middle of the hunt for the conference's final playoff spot, ahead of their only home game in November, against the Packers.

A loss would mean the Vikings could lose only two of their final eight games and still finish with a winning record. It would drop them to 3-6, with the prospect of Packers fans eagerly snapping up tickets to cheer on their team and neutralize U.S. Bank Stadium's home-field advantage.

The Vikings' brand, under Zimmer, evokes a plucky team that does its best work when cornered. They are running out of time to make the results match the messaging.

"I think the same questions, concerns that people watching the games have are the same concerns that every single person in this building has," Thielen said this week. "We want to make this city, this state proud of winning games, the ownership, this organization, we want to make them proud by the way that we play, compete and win.

"I know it's a broken record every week of, 'Yeah, we've got to do this better, we've got to do that.' But we're in this situation now and we've got to find a way out."