Joba Chamberlain went down with a stiff shoulder during a tight pennant race. On a tough night in Texas for the New York Yankees, the latest injury to their pitching staff really hurt.

After the hard-throwing Chamberlain came out in the fifth inning, the Yankees lost 9-5 to the Rangers on Marlon Byrd’s game-ending grand slam off Damaso Marte with two outs in the ninth.

Chamberlain was slated to return to New York today for tests, and manager Joe Girardi said the 22-year-old right-hander probably will miss a turn in the rotation. Anything more than that would be a major blow to the depleted Yankees, who are 2 1/2 games behind Boston for the AL wild-card lead.

“My strength was fine. My velocity was fine,” Chamberlain said. “We’ll have tests just so we can rule out everything. It kind of grabbed and it was a little bit tighter in the fifth inning.”

Already missing Chien-Ming Wang and Phil Hughes from a top-heavy rotation, the Yankees got more bad news when Chamberlain began shaking his arm on the mound.

“He has a little stiffness. We believe it’s muscular,” Girardi said. “We’ll see what the tests reveal. I don’t think it’s serious. I don’t think he’ll be shut down a long time.”

Still, New York is likely to be cautious with the former reliever. Chamberlain said he’s never had a similar problem in his shoulder.

After the game, Girardi also revealed that star closer Mariano Rivera was unavailable for the second consecutive game because of back spasms.

“We were a little short-handed,” the manager said. “He said he felt OK, but I’ve got to hear that he feels great.”

Girardi said he expects Rivera will be ready to pitch tonight.

On a 101-degree night, Marte (0-1) walked three batters in the ninth before Byrd hit a shot into the center-field seats for his fifth career slam and second this season. He was mobbed at the plate by teammates after ending Texas’ 10-game home losing streak to the Yankees.

“I knew it was gone right when it came off the bat,” Byrd said.

Michael Young and David Murphy also homered for the Rangers, who earned their first home win over New York since July 19, 2006. Texas moved five games over .500 (59-54) for the first time this season.

“It was big,” Murphy said. “We’ll ride this for a while.”

The Yankees threatened in the ninth when Johnny Damon hit a two-out double off Eddie Guardado (3-2). Derek Jeter hit a line drive to center, where Josh Hamilton made a tumbling catch to keep the score 5-all.

New York tied it in the eighth on Xavier Nady’s fourth homer in 30 at-bats since joining the team July 26, but the finish was disappointing for the Yankees.

“It was a hard one,” Girardi said.

Young’s three-run shot off Chamberlain in the fifth gave Texas a 5-4 lead.

Byrd hit a two-out single in the fifth before assistant trainer Steve Donohue and Girardi ran onto the field to check on Chamberlain, who pointed at his right shoulder. Then he walked to the dugout and was replaced by Edwar Ramirez.

Chamberlain allowed five runs and eight hits over 4 2-3 innings in his 12th major league start. He yielded three runs or fewer in each of his first 11.

Jason Giambi homered and had three hits. Robinson Cano also connected for the Yankees, who had won 14 of 16 in Texas.



At St. Petersburg, Fla., Cliff Lee (15-2) pitched seven innings to tie for the major league lead in wins and Cleveland improved to 5-0 against the AL East leaders this season.

Tampa Bay’s five-game winning streak ended, but the Rays remained three games ahead of second-place Boston. David Dellucci hit his 100th career homer, off Tampa Bay starter Matt Garza (9-7).



At Kansas City, Mo., Gil Meche won his fourth straight start and Alex Gordon homered to help the surging Royals hold off Boston.

Joakim Soria allowed a run in the ninth before retiring Sean Casey with runners at second and third for his 32nd save in 34 chances. Meche (10-9) struck out nine in six innings for Kansas City, which beat Clay Buchholz (2-7) on a sweltering night to win for the seventh time in eight games.

Dustin Pedroia had a double and two singles, extending his road hitting streak to 25 games — the most by a Boston player since Hall of Famer Tris Speaker 95 years ago.



At Seattle, Raul Ibanez had a grand slam and six RBIs — all in a 10-run seventh inning — and the Mariners staged their biggest comeback of a lost season to stun Minnesota.

Glen Perkins cruised into the sixth with a 6-0 lead and was still up 6-1 with one out in the seventh before Seattle rallied and Ibanez set a club record for RBIs in one inning. It was the most runs the Mariners scored in an inning since Aug. 30, 2003, against Baltimore.



At Anaheim, Calif., Chone Figgins drew a bases-loaded walk from All-Star closer George Sherrill (3-5) with two outs in the ninth, and Los Angeles regrouped after major league saves leader Francisco Rodriguez (1-2) blew a four-run lead.



At Toronto, Roy Halladay (13-8) pitched eight strong innings of four-hit ball to hand Oakland its season-high seventh straight loss. The A’s are a major league-worst 2-14 since the All-Star break, and 9-23 since June 28.