Walking through the locker room after the Vikings' 27-20 loss to the Chiefs on Sunday evening, coach Kevin O'Connell reversed course toward Justin Jefferson's locker. He leaned over and whispered something to the receiver, who had watched the final minutes with a towel over his head on the sideline after a hamstring injury forced him from the game.

"It was tough on him," O'Connell said. "He's the ultimate competitor. We'll get him back as soon as we possibly can. There won't be a better teammate in that locker room during the time [he's out]. Hopefully we have him right back this week."

It was the sort of subdued, somber moment that rarely happened in the home locker room at U.S. Bank Stadium a year ago. Then, O'Connell was flipping game balls to his star receiver after dramatic Vikings victories. The team's mistakes came up mostly in moments of modesty in post-victory news conferences. Jefferson popped up from vicious on-field hits, or emerged from the sideline medical tent ready to return, and the Vikings could exhale.

There were moments on Sunday afternoon, even after the reigning NFL Offensive Player of the Year left the game, when it appeared the Vikings might emerge with the kind of victory over the defending Super Bowl champions that could be conducive to a season turnaround.

The Vikings limited the Chiefs to 333 yards, hitting league MVP Patrick Mahomes nine times while blitzing him more frequently than many teams have. They rallied from a 27-13 second-half deficit with a resourceful scoring drive, and it appeared for a minute late in the fourth quarter as if they would have first-and-goal on the Chiefs 1 after Kirk Cousins' throw to Jordan Addison drew a flag on cornerback L'Jarius Snead from side judge Dominique Pender.

But because of issues that are now becoming themes — costly first-quarter turnovers and missed red-zone chances — the Vikings lost the kind of game they won so frequently last season.

Josh Oliver's fumble on the Vikings' first offensive play gave the Chiefs the ball at the Minnesota 45, setting up Kansas City's opening touchdown drive. The Vikings had to settle for a pair of Greg Joseph field goals in the first half, including one after Cousins threw an incomplete pass through the end zone before K.J. Osborn was ready for the ball.

The Vikings burned one timeout to avoid a delay of game, and another because they had trouble substituting before a fourth-down play where it appeared the Chiefs might go for it. With just over five minutes left, Alexander Mattison dropped a screen pass with room to run toward the end zone, and the Vikings' drive ended two plays later when officials picked up the flag on Sneed after Cousins' fourth-down heave for Addison.

"Very much a disappointed locker room right now," O'Connell said. "We felt like we could come out today and compete with the defending world champs and find a way to get a win here at home. Didn't get off to a very good start with putting the ball on the ground there on the first play. But thought our guys battled, went really the next 59-and-a-half minutes without turning it over and tried to battle through the very end. We have a couple injuries and depth tested. Guys stepped up and tried to compete to the very end. These guys are itching to get back to work already and that's what this is going to be about."

They might have to play, at least in the short term, without Jefferson after he pulled himself from the game in the fourth quarter because of his hamstring injury. O'Connell said it was too early to determine how much time the receiver might miss, adding that he hoped Jefferson would be able to return for next Sunday's game in Chicago. The nature of Jefferson's injury, though, could lead the Vikings and the receiver to be cautious.

"Absolutely love him and what he brings from a competitiveness standpoint and setting a standard," O'Connell said. "It will no question be something we have to work through. But I also have a lot of confidence in our offensive unit to make sure we're right where we want to be when Justin is able to come back."

If Jefferson is forced to miss time, the Vikings could lean more heavily on Addison, who scored for the third time this year, cashing in on a second-quarter crossing route after Mattison's run fake bought Cousins time to sit in the pocket while the rookie receiver worked across the field. The score gave the Vikings a brief 13-10 lead.

"Jordan is the real deal. We hit on that draft pick," Cousins said. "He's a great player. Has great hands and runs great routes. … When Justin goes down, which is tough, he's a special player. There's a lot of confidence that K.J. and Jordan and Brandon Powell and our tight ends and our backs can really fill that gap."

But Oliver's fumble, as well as Mattison's drop and several passes that bounced off T.J. Hockenson's hands, cost the Vikings on a day where they'd talked about making a statement against the defending champs.

"Those guys hoisted the Lombardi Trophy last year. We fought with them every step of the way," Hockenson said. "We had our opportunities; we just couldn't capitalize and I think this team has to have confidence because we have everything out in front of us. We haven't played an NFC North team, and if we can get a lot of those, we're right back in the fight. We've had a rough start, but this can be temporary and we just got to make it temporary."

They are three games behind the Lions in the NFC North, though, having lost a fourth one-score game this season after winning 11 of them last year. The only time the Vikings have lost more than three times in a season at U.S. Bank Stadium was 2020, where no fans were allowed in the stands because of the COVID-19 pandemic. If they lose to the undefeated 49ers in two weeks, the best they can do is finish .500 at home.

"You have to treat them each as individual efforts," Cousins said. "You put this one to bed. You've got to learn from it. You've got to get better and then you go to work getting ready for Chicago, and it's kind of its own entity and you just do that 17 times."

Sunday felt like it could have been the kind of game the Vikings won 13 times a year ago. Instead, it was the fourth loss of a type that's becoming strangely familiar.