Reinjured big toe ends season for 49ers’ Patrick Willis

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Patrick Willis has been playing on a bad wheel for several years. It finally has forced the All-Pro linebacker to make an extended pit stop.

Willis was placed on season-ending injured reserve Tuesday because of a problematic left big toe he re-injured in a win against the Rams on

Oct. 13. Willis, who was initially optimistic he’d return soon, has missed three games and decided to undergo season-ending surgery when the ailment showed no signs of improvement.

Willis’ issues with his toe date back several years, he said, and he likened playing with the injury to driving on bald tires.

“If you like to get on the pedal a little bit, you tell yourself you can’t do that because if you do, you’re going to blow your tire out,” Willis said. “And that’s kind of how I’ve been playing the last few years. … Maybe at certain times people saw something that was uncharacteristic, but that’s all because I was trying to find a way to compensate to be able to find a way to go out there and play.”

Willis was hopeful he could return this season, but he decided to undergo surgery because he feared the injury could shorten a career that has included a Pro Bowl berth in each of his first seven seasons in the league. Willis will turn 30 in January.

“When I hurt (it) in the Rams’ game, it kind of made me a little nervous because I knew what I had been feeling all these years,” Willis said. “I felt like the Lord was talking to me, I felt like he finally said the time is now …

“I feel like I have five or six more great years of football left in my body, but, unfortunately, this toe was telling me otherwise. That was the only thing that was weighing on my mind for a while now.”

The loss of Willis is a significant blow for a defense that’s still without All-Pro inside linebacker NaVorro Bowman, but it’s softened somewhat by the presence of rookie linebacker Chris Borland. In his past two starts subbing for Willis, Borland has 35 tackles, including five for losses, and a fumble recovery.

Patrick Willis averaged 130 tackles from 2007 through 2013 but has just 34 in 2014. Patrick Willis averaged 130 tackles from 2007 through 2013 but has just 34 in 2014. Photo: Scott Strazzante / The Chronicle Photo: Scott Strazzante / The Chronicle Image 1 of / 1 Caption Close Reinjured big toe ends season for 49ers’ Patrick Willis 1 / 1 Back to Gallery

Borland and Michael Wilhoite each will start for the fourth straight game when the 49ers visit the Giants on Sunday. Borland, a third-round pick, was selected No. 77 overall in May.

“I think (Borland’s performance) has exceeded everyone’s expectations in the sense that you never expect to have any player have 17 tackles in a game,” Wilhoite said. “Ten-plus, for any player, is very good. Nobody could ever say they expected him to come in and do what he’s done and dominate in the run game like he has.”

Said Willis: “I’m truly proud of the way he’s playing.”

The 49ers hope Bowman will be playing relatively soon after he tore two ligaments in his left knee in the NFC Championship Game in January. Head coach Jim Harbaugh said Tuesday on KNBR that Bowman “possibly” could return to practice soon, but that decision won’t be made until the three-time All-Pro has another MRI exam.

On Sunday, Bowman told ESPN he’s still experiencing knee pain and was unsure when he could return to practice.

The only backup inside linebacker on the 49ers’ roster is Nick Moody, a 2013 sixth-round pick who has played 10 career defensive snaps, all last year. The 49ers addressed the position Tuesday by re-signing rookie Shayne Skov to their practice squad. Skov, who played at Stanford, spent the offseason with the 49ers and began the season on their practice squad. He was released from Tampa Bay’s practice unit Oct. 21.

Meanwhile, Willis is looking to 2015, when he hopes to take the field with his left foot at full strength for the first time in several years.

“To most people, they might be like, 'Man, maybe Willis is losing a step,’” he said. “But I promise you, physically and mentally, I’m just as good now as I was early. But, unfortunately, the things I need most to make me who I am are my feet.”

Eric Branch is a San Francisco Chronicle staff writer. E-mail: ebranch@sfchronicle.com Twitter: @Eric_Branch