CLEVELAND -- The San Francisco 49ers suffered their first defeat on the field Sunday against the Cleveland Browns and now are waiting to see the severity of the injuries they suffered in the loss.

Wide receiver Deebo Samuel and running back Christian McCaffrey suffered shoulder and oblique/rib injuries, respectively, in the 19-17 loss. The injuries were significant enough that neither player was able to finish the game after departing.

Following the game, coach Kyle Shanahan was unsure of the extent of either injury, though both players will have further testing done Monday.

"We don't know yet," Shanahan said.

Shanahan added the rib designation to McCaffrey's status after he was ruled out in the fourth quarter because of an oblique issue. McCaffrey initially departed in the third quarter but returned to the game for one play -- a 6-yard run with just under 3 minutes left in the third -- before heading to the sideline and then the locker room. The Niners ruled out his return with 10:58 to play.

Samuel's injury happened in the first quarter, though it wasn't immediately clear how or on which play it occurred. His injury was first mentioned at the same time as left tackle Trent Williams', with 3:14 left in the first quarter. Williams had his right ankle rolled up on and returned to the game a couple of offensive snaps later. Samuel spent about 10 minutes in the blue medical tent during the second quarter before heading to the locker room for the rest of the first half. He had two carries for 11 yards before the injury.

McCaffrey departed the game after one carry that was called back for a holding penalty. He had 11 carries for 43 yards and three catches for 9 yards and a touchdown.

Playing without two of their most versatile playmakers, the Niners' offense struggled to find a rhythm after McCaffrey's opening-drive touchdown. Ray-Ray McCloud and Jauan Jennings stepped in for Samuel while Jordan Mason and Elijah Mitchell filled in for McCaffrey. McCloud and Jennings combined for three catches for 30 yards, with McCloud adding two carries for 23 yards. Mason and Mitchell had a combined seven carries for 24 yards, though Mason had five for 27 yards and a touchdown that gave San Francisco a late lead.

"It's more about just getting all the guys ready for it," Shanahan said. "You've got a game plan that's got enough stuff in it but just moving some positions around, we just made too many mistakes."

It didn't help that Williams was also not at full strength after returning from his injury. He missed only a couple of plays while he had his ankle re-taped but he was clearly not at his best, picking up a holding penalty that led to a three-and-out late in the third quarter. Williams was wearing a walking boot on his right foot after the game.

"It didn't feel good at all," Williams said. "It's football. I just tried to fight through it for my teammates. They've got a Hall of Fame rusher over there in 95 [Myles Garrett] and I wanted to get back out there so I could kind of help my team try to contain him. I didn't want to put [backup tackle] Jaylon [Moore] in that position."

Quarterback Brock Purdy shouldered the blame for not doing enough to make up for the missing superstars. He finished his worst professional performance 12-of-27 for 125 yards with a touchdown and an interception for a passer rating of 55.3, taking his first regular-season loss as a starter. As the Niners await a further diagnosis on McCaffrey, Samuel and Williams, Purdy said it will be up to him to help pick up the slack.

"They're really good playmakers so it hurts," Purdy said. "But at the same time, we have got guys to be able to come in and make plays too. That's on me being able to help out the guys like Ray-Ray and JJ who are going to play more, Elijah coming in. I've got to do a better job with communicating with them in the huddle, giving them some sort of expectation of what's to come in terms of the play and stuff.

"That's something I've got to be better at. ... I'm confident whoever comes in, even if Deebo and Christian aren't able to go, we have got good players."