Ray McDonald tore a muscle at the top of his right biceps when he sacked Matt Schaub during the third quarter of Sunday's 34-3 victory over the Houston Texans. He was told he could play with the injury as long as he can stand it.
"It's going to be sore but I should be fine," McDonald said. "I've got all my strength and I'm fine with that."
The injury for McDonald is the latest in a series of ailments for San Francisco's defensive line this season. Ian Williams went on injured reserve after he broke his left ankle during a loss to Seattle in Week 2.
In addition, rookie defensive tackles Tank Carradine and Quinton Dial are on the non-football injury reserve list, though both could be cleared to start practice shortly.
McDonald and Justin Smith are the only two defensive linemen to start all five games.
"He's one of the toughest guys I know," 49ers nose tackle Glenn Dorsey said of McDonald. "I know that whatever he can do to keep going, he'll do it."
The 49ers have been able to remain competitive, with Dorsey filling in for Williams and Tony Jerod-Eddie finishing last week's game for McDonald.
"The coaches and scouts go out and find players who can contribute to the team," McDonald said. "Tony did pretty good. He did what he was supposed to do."
Jerod-Eddie had an interception.
"You have moments like that where you think 'That could have been my interception,'" McDonald said. "We have a saying that we're always happy for another guy's success."
McDonald said the tear will need surgery following the season.
"I'm able to use it, so that's a good sign," he said. "I'll know more as the week goes on."
McDonald, in his seventh season, hopes to practice with the team on Wednesday to test the injury.
"You always want a guy like that playing next to you," Dorsey said. "He's a tough guy."
Like Jerod-Eddie, Dorsey was prepared when his number was called.
"It's about being resilient," he said. "It's about being prepared so that when your time comes, you're ready to play at a high level."
Carradine, 11 months removed from surgery to repair an ACL tear in his right knee, feels as if he's nearly ready.
"I still have to wait for the say-so, but I am ready to get back on the field," Carradine said. "All I've been able to do is run and lift, so I had no choice but to get better. I've been watching a lot of game film and studying the playbook so I can be up to speed and able to do what I used to do."
Follow Editor in Chief Chris Biderman on Twitter.