San Francisco 49ers wide receiver Deebo Samuel has been hospitalized due to fluid in his lungs, head coach Kyle Shanahan revealed on Monday afternoon.

It’s unclear how long he will be sidelined, or if he will be able to play in Sunday’s game against the Dallas Cowboys.

Shanahan said that Samuel first started dealing with symptoms on Sunday morning, and that he was having trouble breathing during their 28-18 loss to the Kansas City Chiefs. Samuel was pulled from the game in the second quarter, and did not return. He was then admitted to a local hospital that night.

Samuel has racked up 335 yards and one touchdown on 20 catches this season, his sixth with the 49ers. He did not make a catch and wasn’t targeted in Sunday’s game at Levi’s Stadium. He was also seen on the sidelines during that contest wearing an oxygen mask, and then he returned to the field in street clothes in the second half.

He was questionable leading up to the game with an illness, but specifics weren’t known.

Samuel’s illness is the latest blow to the 49ers’ offense this season. Fellow wide receiver Brandon Aiyuk tore both his MCL and ACL in Sunday’s loss, too, and he’s set to undergo season-ending surgery in the near future. Aiyuk’s knee bent in awkwardly after he made a catch in the middle of the field, and he had to be carted off just before halftime.

Along with the two wide receivers, running back Christian McCaffrey has yet to play this season while dealing with calf and Achilles injuries. Rookie wide receiver Ricky Pearsall made his debut on Sunday after missing the first six games of the season after he was shot in the chest.

The 49ers dropped to 3-4 on the season after Sunday’s loss. They’ll host the Cowboys next on Sunday night.