Minneapolis ? Alex Smith and the Kansas City Chiefs were finally starting to find a rhythm without star running back Jamaal Charles. The yards were coming in bunches, and a six-point deficit suddenly didn’t seem so bad.

Then left tackle Donald Stephenson inadvertently knocked the ball out of the grasp of rookie running back Charcandrick West, a fitting end to a mistake-prone day for the Chiefs.

Smith threw for 239 of his 282 yards in the second half, including a 42-yard catch-and-run by Albert Wilson that cut Minnesota’s lead to just three points midway through the fourth quarter. But West fumbled in Minnesota territory on the next possession, and Smith missed on two deep throws in the final two minutes as the Chiefs fell to 1-5 with a 16-10 setback.

“We were very confident. The fumble killed everything,” said West, who had nine carries for 33 yards. “A fumble at that point of the game is crucial. Gotta hold on to it.”

The Chiefs also committed eight penalties for 95 yards and lost defensive end Mike DeVito and receiver Jeremy Maclin to concussions.

It took plenty of time for the Chiefs’ offense to find itself after losing Charles for the season last week because of a knee injury. The unit managed 51 yards while the Chiefs were charged with 50 yards in penalties in the first half as the Vikings jumped to 10-0 lead.

Coach Andy Reid called the sloppiness “completely unacceptable.”

“There were so many self-inflicted things,” Smith said. “The penalties, you can’t even get going when you’re just going backwards. Especially against a team like that on the road. It makes it impossible.”

The yellow flags flew all afternoon, most critically against the Chiefs. Cornerback Steven Nelson was called for roughing the passer on a third-and-6 incompletion midway through the second quarter, extending a drive that ended with Teddy Bridgewater’s short touchdown pass to Kyle Rudolph that put the Vikings up 10-0.

The Chiefs blew their best chance late in the third quarter, when Anthony Sherman and West were stymied on third-and-1 and fourth-and-1 at the Minnesota seven. Both Reid and West maintained that the running back’s knee never touched the ground, but the play was not reviewable.

The defense did keep the Chiefs in the game, though. Ron Parker intercepted Teddy Bridgewater in the end zone to stop one drive and Marcus Peters picked him off in the fourth quarter to set up Wilson’s score on a screen pass.

The Chiefs also held Adrian Peterson to 60 yards rushing on 26 carries, a paltry 2.3 yards per attempt.

Kansas City had two cracks to take the lead in the last five minutes. The first drive ended with West’s fumble and the second with consecutive incompletions to Wilson deep down the field.

“Gotta hit those,” Smith lamented.

Bridgewater completed 17 of 31 passes for 249 yards and a touchdown to Kyle Rudolph. Vikings rookie Stephon Diggs added seven catches for 129 yards in his first career start.

Travis Kelce had five catches for 88 yards for the Chiefs, all of which came in the second half.

“In the second half we put ourselves in a position to win the game and we didn’t finish it,” Reid said. “Way too many penalties, way too many sacks, turnovers, all those things. Can’t do that.”

Reid said the performance in the final two quarters showed that the team has the ability to have success without Charles, but the prospects after being 1-5 six weeks into the season remains daunting.

“As dark as it is, you want to sulk,” Smith said. “There’s no time for any of that. You’ve gotta go. It keeps moving. The ball keeps moving.”

NOTES: Maclin was injured while diving to try to make a catch in the fourth quarter. He started to walk off the field, but had to stop halfway to the sideline to take a knee again. … NT Dontari Poe (ankle) and LB Josh Mauga (Achilles tendon, groin) did not play. … Knile Davis had just 13 yards on five carries. … Cairo Santos kicked a 48-yard field goal in the fourth quarter.