Rookie lineman ignored injury
Right tackle Erik Magnuson knew something horrible had happened Sunday when he heard a pop in his foot, but he also knew he wasn’t coming out of the game.
Magnuson, an undrafted rookie making his second career start, played through a severe injury for most of the final three quarters of a 24-13 loss to the Seahawks. How severe? On Wednesday, the 49ers placed him on injured reserve with a foot sprain that Magnuson says also involves a torn ligament.
“I immediately knew something was wrong because I felt it pop,” Magnuson said. “My first reaction was ‘Man, I broke my foot.’ But I had just had them tape over my shoe and tape my foot real tight so I couldn’t feel it. I didn’t really think there would be long-term consequences from it if I kept playing.
“I figured the damage was already done, but looking back on it I think it probably would have been smart to get some help.”
Magnuson stayed in the game because the 49ers were shorthanded — he was filling in for injured starter Trent Brown — and, well, he was in the midst of a rare opportunity.
“I knew that unless I was unable to walk I needed to stay in the game because we were short on offensive linemen,” Magnuson said. “I got the opportunity to start, I’m a rookie, I wasn’t going to come out for something I was able to play through.”
On Monday, after the severity of his injury was revealed, Magnuson received thanks and kudos from left tackle Joe Staley and center Daniel Kilgore, the offensive line’s elder statesmen. Magnuson’s pain was compounded by the fact that he was facing Pro Bowl defensive lineman Michael Bennett, who had one sack and two quarterback hits.
“It was a big challenge,” Magnuson said. “He’s very, very good player and very unique in the way he plays. So that it made it very difficult.”
Magnuson, who is expected to compete for a spot at guard or center next season, could be in a walking boot for up to eight weeks. He said he will be ready for the offseason program in April. Injury report: Head coach Kyle Shanahan said Brown took increased snaps in practice Friday, but he will be a game-time decision for Sunday’s game in Chicago.
If Brown misses his second straight game, he will likely be replaced by Zane Beadles, who also plays guard and had been the team’s only backup center. On Wednesday, the 49ers signed guard/center Tim Barnes, which suggested Beadles was being eyed to play tackle, if necessary.
Meanwhile, Shanahan said safety Adrian Colbert (thumb) and cornerback Ahkello Witherspoon (ankle) will also be game-time decisions. Witherspoon was limited in practice Friday after he missed Thursday’s session. He was injured in practice Wednesday when he landed awkwardly when contesting a pass to Aldrick Robinson.
Quarterback C.J. Beathard (knee, hip), who missed practice Wednesday, was not listed on the injury report and will serve as Jimmy Garoppolo’s backup Sunday. Eric Branch is a San Francisco Chronicle staff writer. Email: ebranch@sfchronicle.com Twitter: @Eric_Branch