SEATTLE (AP) _ Butch Henry and Mark Leiter, who were counted on this spring being key members of the Seattle Mariners' pitching staff, will undergo surgery on their shoulders.

Both probably will miss the rest of the season.

The team announced on Monday that Henry, their No. 4 starter with a 2-0 and a 4.63 ERA, has a torn labrum in his left shoulder.

The Mariners said Leiter, a setup man in their bullpen this season, has a torn rotator cuff in his right shoulder.

Henry, 30, will undergo arthroscopic surgery on Thursday that will cause him to miss 4-6 months. He could possibly rejoin the Mariners' staff in September.

Henry started Seattle's 22-6 victory over Detroit Thursday, but came out in the fifth inning with tightness in his left shoulder.

Leiter, 36, will have surgery next week, causing him to be sidelined for 9-12 months.

Leiter was placed on the 15-day disabled list Sunday with what was diagnosed as a strained right shoulder. In two appearances this season, Leiter pitched 1 1-3 innings and had a 6.75 ERA.

He had to leave Saturday night's game against Toronto.

The Mariners will transfer Leiter from the 15-day to the 60-day disabled list, put Henry on the 15-day disabled list and purchase the contract of left-hander Sean Spencer from Triple-A Tacoma on Wednesday.

At Tacoma, Spencer was 0-0 with a save and an 0.73 ERA in eight games and 12 1-3 innings.

Henry was signed by the Mariners as a free agent Dec. 16 after pitching briefly in Boston last season. He was on the disabled list most of last season while recovering from surgery for a torn anterior cruciate ligament in his left knee.

In 1996, he missed the entire season while recovering from ligament replacement surgery on his left elbow, Tommy John surgery.

Leiter came to the Mariners Nov. 9 in a trade with Philadelphia for left-hander Paul Spoljaric. Last season, Leiter was 7-5 with a 3.55 ERA in 69 relief appearances with the Phillies.