The Associated Press

CHICAGO - Andy Pettitte went back on the 15-day disabled list Monday because of a strained muscle in his left forearm.

The Houston left-hander was hurt Wednesday during a game against the Chicago Cubs. He's eligible to be activated June 11.

Pettitte, who signed a $31.5 million, three-year contract with Houston following nine years with the New York Yankees, also was on the disabled list from April 7-29.

"He doesn't have to make himself get back on the mound. He has to do it within his own timeframe, with how his arm feels," Astros manager Jimy Williams said before Monday's game.

Pettitte has made just seven starts in the first two months and is 4-1 with a 3.38 ERA.

Houston activated right-hander Chad Harville, who'd been put on the DL May 6 because of a strained right hamstring.

CUBS: Mark Prior is ready to pitch. On the disabled list since spring training, Prior is scheduled to make his season debut Friday for the Chicago Cubs against the Pittsburgh Pirates.

"It hurts me more than anything to miss two months because you know you are letting your teammates down and your friends," Prior said Monday.

After being sidelined with an inflamed right Achilles' tendon and sore right elbow, Prior was impressive in his third rehab start Sunday when he allowed two runs and three hits while striking out 10 in 5 1-3 innings for Triple-A Iowa.

Prior will be on a pitch limit.

RED SOX: Nomar Garciaparra went 2-for-3 Monday for Triple-A Pawtucket in his second minor league rehabilitation game.

Garciaparra singled in the first and third innings, walked in the fourth and left the game after fouling out to the catcher in the sixth.

SHORT HOPS: The Red Sox collected money on Monday to buy food and medicine for flood victims in the Dominican Republic, the homeland of stars Pedro Martinez, Manny Ramirez and David Ortiz.

• San Diego activated right-handed reliever Antonio Osuna from the 15-day disabled list Monday. Right-hander Brian Sweeney was optioned to Triple-A Portland.

• Marlins pitcher Josh Beckett was placed on the 15-day disabled list Monday because of a blister on the middle finger of his throwing hand. Reliever Ben Howard was recalled from Triple-A Albuquerque.