SAN FRANCISCO — The San Francisco 49ers placed right tackle Jonas Jennings on injured reserve Tuesday for the third time in his four seasons with the club.

Jennings underwent surgery Tuesday on his dislocated right shoulder, which has kept him out of action since it occurred in Week 2 against Seattle. He dressed but didn't play in the 49ers' (3-7) last two games, and the club eventually decided to scrap another season for a $36 million tackle who has missed 35 games with injuries since signing with San Francisco in 2005.

"He was cleared to play and practice, and he tried," 49ers general manager Scot McCloughan said. "He tried, and he was active the last two weeks in an emergency situation. He had the harness on, (but) it wasn't getting any better rehabbing anymore. Surgery was inevitable."

The 49ers signed tackle Jacob Bender off New England's practice squad to replace Jennings on the roster. Bender was a sixth-round draft pick of the New York Jets last year.

Jennings played in just 23 of the 49ers' 58 games since leaving Buffalo as the first big free-agent signing of former coach Mike Nolan's tenure. Jennings also never made it through a full 16-game season in four years with the Bills.

He missed 13 games in his debut season in San Francisco with another injury to his shoulder, which has required three surgeries. Jennings also missed all but five games last season with an ankle injury and other various ailments.

Barry Sims took over for Jennings, but the veteran sprained his left ankle last month in a loss to the Seahawks. Adam Snyder played the last two games at right tackle, and Sims is expected to be active for Sunday's game at Dallas.

"If we didn't have Snyder, the way he's playing at right tackle, (and) we didn't have Sims to back it up, we could have kept (Jennings) as an emergency tackle the rest of the year," McCloughan said. "But because of the numbers we have, we felt fine doing the surgery now."

Jennings probably will need six months to recover from his latest surgery, and it seems unlikely he'll be with the 49ers by then. With two seasons remaining on his lucrative contract, the club's patience finally might be exhausted for its high-priced bust.

McCloughan isn't eliminating any of his options just yet, however.

"Everybody is built different, and some guys are more injury-prone than others," McCloughan said. "But there's no reason why he can't come back from this once rehab is over and play again. There's no reason whatsoever."