BOSTON (AP) _ The Boston Red Sox added depth to their starting rotation on Thursday, purchasing left-hander Pete Schourek from the Houston Astros.

Schourek, 29, was 7-6 with a 4.50 ERA in 15 starts for the Astros this season, winning four of his last five decisions. He had his best year in 1995, when he went 18-7 for Cincinnati, but since having elbow surgery his endurance has been limited.

And, when the Astros acquired Randy Johnson last week, Schourek became expendable. The deal, for an undisclosed amount of cash, creates space on the Houston roster for lefthandeder Billy Wagner, who's expected to be activated from the 15-day disabled list for Friday night's game against the Phillies.

``Pete did a great job for us this year in helping us get where we are,'' Astros general manager Gerry Hunsicker said. ``Rebounding from elbow surgery is difficult at best, and there were some days he went out there and was not at 100 percent.

``This was not an easy decision for us to make. We're going to miss Pete's experience down the stretch, but we appreciate his efforts and wish him all the best in Boston.''

Schourek has a career mark of 57-52 with 304 walks and 600 strikeouts. Schourek will join the Red Sox in Texas on Friday, and he could start against the Rangers on Sunday.

``He's been a winning major league pitcher and adding him to our ballclub gives us additional experience,'' Red Sox general manager Dan Duquette said in a conference call. ``Pitching depth will be a key for us for the rest of the season.''