Mark Prior walked off the mound in the second inning with his head down and his status for his next start up in the air.

The right-hander left with discomfort in his elbow after pitching just 1

innings Thursday night, putting the Chicago Cubs in a somber mood after a 4-1 comeback win over Milwaukee.

"I don't know what I got going right now," Prior said.

Prior, scheduled for an MRI today, already missed the first two months of the season with a sore right Achilles' tendon and tender elbow.

"You can't get any more worried than sick to your stomach," Cubs manager Dusty Baker said.

With one out in the second, Prior got Milwaukee's Chad Moeller to hit a grounder to Derrek Lee at first. Prior started off the mound to go to first before Lee made the play unassisted.

But trainer Dave Groeschner and pitching coach Larry Rothschild knew something was wrong with Prior, quickly going out to the mound to talk to him. He was then replaced by Glendon Rusch.

"It's something I've been dealing with off and on since it happened in spring training," said Prior, who made just his eighth start. "Hopefully we can get some answers this time on what it really is. To be honest, I can't tell you where I'm at or where I'm going to be."

At Phoenix, Shawn Green hit a grand slam in the eighth inning off Randy Choate, who took over after Randy Johnson struck out nine in seven scoreless innings.

At Denver, Shawn Chacon hit J.T. Snow with a pitch with the bases loaded for the go-ahead run in San Francisco's four-run ninth.Colorado led 4-3 behind five-plus solid innings from Jason Jennings, but Chacon (1-6) couldn't hold the lead in the ninth.

At Atlanta, Marcus Giles doubled twice in his first game in two months and Jaret Wright (7-5) won his fifth straight decision.

At New York, pitcher Roberto Hernandez couldn't handle Ty Wigginton's decisive bases-loaded comebacker in the 11th inning..Wigginton hit the ball back to Hernandez (1-3), who knocked it down with his bare hand but he bounced his throw home as pinch-runner Vance Wilson slid across the plate.

At Cincinnati, Albert Pujols and Scott Rolen hit two-run homers to lead St. Louis.

And even though he allowed a leadoff single to end his outing, the former Cuban star felt he never pitched better.Jose Contreras allowed four hits and struck out seven, and Alex Rodriguez hit two of the New York Yankees' five home runs - their only hits - in a win at Detroit.

At St. Petersburg, Fla., Baltimore's David Newhan hit a tiebreaking, two-run triple in the seventh inning.

At Kansas City, Mo., Mike Sweeney's RBI single in the first ended the Royals' 31-inning scoreless drought against the Twins.

At Seattle, Justin Leone hit his first major league homer - a two-run shot - to back Joel Pineiro (5-10) and help Seattle end a nine-game losing.

Oakland, Calif., Rich Harden (4-5) allowed four hits in eight innings, and Eric Chavez had a home run and Bobby Crosby an RBI double against Jon Garland (7-6).

At Anaheim, Calif., Darin Erstad homered and drove in three runs, and Chone Figgins also had three RBI for Anaheim.