The San Francisco 49ers lost standout receivers Brandon Aiyuk and Deebo Samuel during Sunday's 28-18 loss to the visiting Kansas City Chiefs.

San Francisco coach Kyle Shanahan said after the contest that the club fears Aiyuk sustained a major knee injury.

"We're worried it's an ACL," Shanahan said. "Not confirmed yet. We''ll find out for sure tomorrow."

Aiyuk was carted off with a right knee injury in the final minute of the first half. Samuel played briefly early in the game before exiting with an illness.

The 49ers also were without receiver Jauan Jennings, who didn't practice all week and missed the game with a hip injury.

Aiyuk had two receptions for 23 yards before departing. He was injured when he caught a 15-yard pass and was hit by two Kansas City defenders, with the blow from Chamarri Conner causing Aiyuk's right leg to bend backward.

Samuel was seen receiving oxygen on the bench in the first quarter. He didn't touch the ball before departing. It marked his second missed game of the season.

"It was him struggling to breathe that ultimately shut him down," Shanahan said of Samuel.

Jennings leads San Francisco with 404 receiving yards. He also has 25 receptions and three touchdowns.

Aiyuk has 25 catches for 374 yards and hasn't caught a touchdown pass. He staged an offseason holdout before accepting a four-year, $120 million contract extension in late August.

Samuel has 20 catches for 335 yards and one touchdown and also has 51 rushing yards and another score on the ground.

Rookie Ricky Pearsall was active for the first time after being placed on the 53-man roster on Saturday, and the first-round pick had three receptions for 21 yards. Pearsall was shot in the chest during a robbery attempt in San Francisco on Aug. 31.

--Field Level Media