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NEW YORK -- Jorge Posada was long gone by the end of the game, sent away for an MRI on his tight right calf. When the ninth inning started, Joba Chamberlain emerged from New York's bullpen because Mariano Rivera was unavailable due to stiffness in his left side.

It didn't cost them on this night, but the injuries are beginning to pile up for the Yankees.

CC Sabathia pitched eight strong innings in another sterling start against Baltimore, Randy Winn hit a three-run homer and banged-up New York beat the Orioles, 4-1, on Monday.

"I think any time you start seeing guys get a little bit nicked up it's a concern," Yankees manager Joe Girardi said.

Sabathia allowed one run -- Matt Wieters' second-inning homer -- and six hits while improving to 11-1 with a 2.52 ERA in 16 career starts against Baltimore. The big left-hander also beat the Birds in his previous outing, pitching into the eighth inning of an 8-3 win at Camden Yards last Wednesday.

"I was trying to find it a little earlier in the game," Sabathia said. "After we scored some runs, I was able to settle down and just lock it in and try to throw the ball over the plate and make them swing early in the count."

Alex Rodriguez singled and scored during a four-run fourth in his return to the lineup after a day off, but Posada was replaced at catcher by Francisco Cervelli before the sixth. Girardi said Posada's calf started bothering him during his second at-bat, as if someone hit him in the leg. An MRI revealed a mild strain, and the Yankees said he was day to day.

"My guess is we'd be without him for a couple of days," Girardi said before the test results came back. "He'd be an emergency catcher, so maybe you're looking at Friday again."

New York is carrying 13 pitchers on its 25-man roster, so it could send down a reliever in the next couple of days and add a catcher or outfielder. Right-hander Mark Melancon was brought up when All-Star center fielder Curtis Granderson went on the 15-day disabled list Sunday with a strained groin.

Rivera felt some tightness in his side on Saturday but played catch Monday and will try to throw off a mound Tuesday.

"I'm not worried at all," he said. "Like I said, I threw today and it felt good but I didn't want to push it."

Chamberlain finished for his second career save and first since Sept. 23, 2007, against Toronto.

Jeremy Guthrie (0-4) turned in a solid start for Baltimore, except for the rocky fourth. The right-hander pitched seven innings of six-hit ball after getting knocked out in the fifth in his previous outing, also against New York.

"I thought that he pitched a good game and went right at them," Orioles manager Dave Trembley said. "It was a very good approach, but unfortunately that one inning got him."

Guthrie drew some criticism from Girardi when he plunked Posada with a pitch on Wednesday, sidelining the switch-hitter for two starts with a swollen right knee. But Guthrie, who also hit New York first baseman Mark Teixeira with a pitch during spring training, exhibited solid control in this one, with just two walks on his line.

Wieters' third homer gave Baltimore an early lead but the Orioles, who were coming off a three-game sweep of Boston, couldn't hold on.

Nick Swisher, who went 3 for 3, drove in Rodriguez with a two-out single in the fourth. Brett Gardner then singled before Winn hit a 1-0 pitch into the Yankees' bullpen in right-center for his first homer since April 25, 2009, for San Francisco at Arizona.

"We were trying to go outer third and if you look at the replay, it was inner third, right where a lefty likes it," Guthrie said.

Winn's first homer with New York came on the same day good friend Dave Roberts announced he is being treated for Hodgkin's lymphoma. Winn played with Roberts for two seasons with the Giants and said he was confident his buddy would pull through.

"He's a fighter," Winn said. "I have no doubt in my mind that everything is going to work out for the best."

Sabathia (4-1) allowed a season-high 11 hits in his last start against Baltimore but was much sharper at home in the opener of a three-game set. The only hiccup he had came in the seventh, when Girardi visited him on the mound after he exchanged words with plate umpire Bill Hohn in a dispute over the strike zone.

"In the heat of the battle, you get a little frustrated," Sabathia said. "But a couple years ago I probably would have lost it a little more than I did. Me getting older and being able to control my emotions definitely helped me out tonight."

Game notes

RHP Javier Vazquez's next start for the Yankees has been pushed back to Monday. ... Orioles RHP Koji Uehara (strained left hamstring) was scheduled to pitch for Triple-A Norfolk on Monday night in his fourth rehab game. He will be off for the next two days and could rejoin the team in Minnesota. "We'll see after the reports we get tonight, and see where we go from there," Trembley said before the game.