SANTA CLARA, Calif. – Already missing one of their top three receivers, the San Francisco 49ers lost wideouts Deebo Samuel and Brandon Aiyuk to an illness and a right knee injury, respectively, on Sunday against the Kansas City Chiefs.

The most immediate concern was Aiyuk’s injury. With 48 seconds left in the second quarter, Niners quarterback Brock Purdy found Aiyuk between two Chiefs defenders for a gain of 15 yards. Chiefs defensemen Chamarri Conner and Trent McDuffie converged on Aiyuk when he took a low hit, leaving his knee in a precarious position.

Aiyuk remained down as Nine’s medical staff came out to help before he could get up, slowly limped to the sideline and headed to the medical tent. He went to the locker room shortly afterwards and a return was ruled out as the third quarter started.

Aiyuk’s injury comes after Samuel fell ill on Sunday morning. Samuel didn’t do much during warm-ups and the team announced he was sick but expected to play.

Samuel walked onto the field just before the game started and took part in the toss, but moved slowly. He didn’t have a catch or carry before his day ended.

Entering Sunday, San Francisco was already missing Jauan Jennings, who suffered a hip injury in last week’s win against the Seattle Seahawks.

Without their top three receivers, the 49ers are limited to veterans Chris Conley and Ronnie Bell and a pair of rookies, Ricky Pearsall and Jacob Cowing.

Pearsall, the No. 31 overall pick in April’s NFL draft, is playing in his first regular-season game, 50 days after he was shot in the chest during an alleged robbery attempt.