PHOENIX — Before throwing a single pitch in the regular season, San Francisco’s Matt Cain wound up on the disabled list.

The Giants said Tuesday that Cain has a flexor tendon strain in his right forearm, and put the 30-year-old right-hander on the DL retroactive to April 4.

Cain will return to San Francisco for further evaluation. He could miss a few weeks, manager Bruce Bochy said before Tuesday’s game against the Arizona Diamondbacks.

“It’s unfortunate for Matty,” Bochy said. “He’s worked hard to get back on the mound and he’s had a little hiccup there, but hopefully it won’t be too long. It’s hard to say. Two, three weeks, we’re hoping.”

Cain was scratched from his scheduled start on Wednesday, and the Giants said an MRI revealed Cain does not have ligament damage in his forearm.

A three-time All-Star, Cain did not pitch after July 9 last season and had surgeryAug. 12 to remove bone chips. He had a 5.40 ERA in four spring training starts, allowing 15 hits in 11 2-3 innings with seven strikeouts and three walks.

San Francisco recalled right-hander Chris Heston from Triple-A Fresno and is slated to start Wednesday against the Diamondbacks.

Right-hander Jake Peavy was scheduled for a bullpen session Tuesday as he deals with back soreness and is in line to start on Sunday at San Diego if he is cleared by the team’s medical staff.