Giants' rotation would be hard to crack

The Giants have one of baseball's best and most reliable starting rotations. Tim Lincecum, Barry Zito, Matt Cain, Jonathan Sanchez and Madison Bumgarner are durable and all under team control for at least two more seasons.

Generally, that is a good thing, but it is creating one small headache for the front office.

The Giants need a so-called sixth starter who can work out of the bullpen or go to the minors and be ready if one of the regular five goes down. Manager Bruce Bochy said last weekend that he and general manager Brian Sabean recognize the need for rotation insurance and are weighing options "both internal and external."

Problem is, they have no experienced in-house candidates, and signing a free agent is not easy when the next full-time opening for a spot in the rotation might come in 2013, when Sanchez is eligible for free agency.

Ideally, the Giants would sign a seasoned pitcher who needs to prove himself after an injury or a decline in performance, most probably to a no-risk minor-league contract with an invitation to spring training.

Former Padres right-hander Chris Young, who reportedly is close to signing with the Mets, is a good example. Others still on the market include Jeremy Bonderman, Kevin Millwood and Rodrigo Lopez - but the Giants are not an attractive option because their rotation is set.

"It's a bit intimidating for players on the top of that list to come here," Giants executive Bobby Evans said Monday. "A lot of these guys are looking for a fourth or fifth spot in the rotation."

Last year, the Giants signed former Cardinals and Cubs right-hander Todd Wellemeyer to a minor-league contract. He won the fifth starter's job in spring training, made 11 starts and went 3-5 before he pulled a quadriceps muscle running out a grounder in Cincinnati in early June. Shortly thereafter, Bumgarner took Wellemeyer's spot.

This year, the Giants do not have even a Wellemeyer in camp. The starters on the spring training invite list include the less-experienced Casey Daigle, Shane Loux and Ryan Vogelsong.

The only starting prospects on the 40-man roster are 25-year-old Henry Sosa, who struggled with his stuff and maturity at Triple-A Fresno last season, and 23-year-old Clayton Tanner, who spent all of 2010 at Double-A Richmond, Va. Both are probably headed to Fresno.

The Giants, anticipating this need, have talked to Dan Runzler about converting from relief to starting.

Besides searching for a pitcher, the front office has been discussing contracts with six arbitration-eligible players, trying to cobble deals before players and teams exchange salary figures today. The Giants are believed to be considering one-year contracts for Sanchez, outfielders Cody Ross and Andres Torres, and relievers Javier Lopez, Santiago Casilla and Ramon Ramirez.

E-mail Henry Schulman at hschulman@sfchronicle.com.

This article appeared on page B - 1 of the San Francisco Chronicle