The Giants’ rotation, already dotted with question marks, will have another as the team starts spring training in six weeks: the health of Tim Hudson’s right ankle.

The Giants revealed Tuesday that Hudson underwent surgery Friday to remove bone spurs from the ankle. Recovery time is eight weeks, which means the 39-year-old is expected to be on restricted duty and behind the other starters when pitchers and catchers report to spring training Feb. 18.

Assistant general manager Bobby Evans said the team expects Hudson to be ready for Opening Day, but acknowledged, “This is definitely a setback as far as his offseason conditioning program. There’s no way around it. The hope is it’s a setback that can be minimized.”

Hudson believes it will. He said by phone from his Alabama home that when he gets to Arizona, he hopes to “pick up where I normally am from a throwing standpoint. I’m assuming in six to eight weeks, it’ll be like nothing happened to it.”

Hudson signed a two-year, $23 million contract before the 2014 season. He started well, then tailed off considerably. Some of that was attributed to the conditioning he had to forgo last offseason while rehabilitating the same ankle after a devastating injury and surgery in August 2013.

Beyond that, Hudson said, the ankle started bothering him during the middle of the 2014 season, about the time his numbers declined. Hudson said he knew he had spurs in the ankle when he had the 2013 operation, but the surgeon did not want to shave them at the time lest Hudson be saddled with another layer to an already complex recovery.

Hudson revealed that he required cortisone shots midway through 2014 and the ankle felt much better toward the end of the year and in the postseason.

But once he went home after the World Series championship parade, began his normal conditioning and went off anti-inflammation drugs, the pain recurred and he decided to have the operation, which Dr. Bob Anderson performed in Charlotte, N.C.

“It’s something I didn’t want to deal with during the season,” Hudson said. “We thought it was a good idea to get them taken out before season starts and hopefully it won’t be a problem.”

He expects to resume his conditioning in about a week.

Hudson’s surgery adds to a long list of Giants’ rotation questions after their unsuccessful bid to sign Jon Lester:

•How will Madison Bumgarner’s arm respond to throwing 270 innings in 2014?

•Will Matt Cain be fully healthy and return to top-of-the-rotation form after bone-chip operations in his right arm and ankle?

•Can Tim Lincecum defy recent history and be a consistent, effective starter again?

•Which Jake Peavy will the Giants get, the one who struggled so badly for the Red Sox or the one who thrived in San Francisco last year?

Despite these questions, Evans said the front office had not been focused on adding a major-league starter since re-signing Peavy, and that will not change with Hudson’s surgery, although the team continues to seek more depth throughout the roster.

“We have five starters,” Evans said, though he added that something like Hudson’s surgery “always gives you the reality check that, hey, nobody’s invincible and you definitely have to have backup plans in the event things don’t go according to plan.

“That’s what the farm system is for. That’s what your nonroster invites are for. That’s where (Yusmeiro) Petit is so valuable.”

Henry Schulman is a San Francisco Chronicle staff writer. E-mail: hschulman@sfchronicle.com Twitter: @hankschulman