--1B Kevin Youkilis left Monday night's game in the sixth inning with tightness in his lower back and was replaced by 1B Jeff Bailey. The cleanup hitter appeared to hurt himself while swinging the bat in a fifth inning at-bat and will be evaluated by the training staff Tuesday. Youkilis leads the major leagues in batting average, slugging percentage and on-base percentage, and the Sox can ill afford to lose him for any length of time.

--OF Rocco Baldelli played in a minor-league rehab game for Class AAA Pawtucket on Monday night and went 0-for-3 with an RBI and a strikeout. Baldelli, on the 15-day disabled list with tightness in his left hamstring, hit in the leadoff spot and played designated hitter for the PawSox. Baldelli is scheduled to play for Pawtucket again on Tuesday night, but it hasn't been determined whether he'll again DH or play in the outfield. "This is the first time I've played since I hurt my hamstring, so I was going to go out there pretty aware of it and being sure of myself and making sure it feels good before I get on it really hard," Baldelli told the Providence Journal. "It felt fine, everything was fine. I got to see some pitching, which I was happy about. I came out feeling good. I can go home pleased tonight. ... It was good to get back on my feet."

--OF Jason Bay has been a certified Yankees killer in the early part of 2009, and did it again Monday night when he lifted a majestic two-run bomb in the seventh inning to add valuable insurance runs. Bay is hitting .600 (9-for-15) with two home runs and seven RBIs in four games against the Yankees this season, and has been at his best in the late innings of those matchups.

MEDICAL WATCH:

1B Kevin Youkilis (back) came out of the game May 4 and was scheduled to be examined May 5.

OF Mark Kotsay (back surgery in January 2009) went on the 15-day disabled list retroactive to March 27. He began a rehab assignment with Class AAA Pawtucket on May 2, but left the May 3 game with a strained right calf.

OF Rocco Baldelli (strained left hamstring) went on the 15-day disabled list April 21. The injury was considered minor. He began a rehab assignment with Class AA Pawtucket on May 4.

RHP Daisuke Matsuzaka (mild right shoulder strain) went on the 15-day disabled list April 15. He threw on flat ground April 21 and threw long toss April 27. He will make a rehab start for Class AAA Pawtucket on May 5.

SS Jed Lowrie (sprained left wrist) went on the 15-day disabled list retroactive to April 12. He had surgery April 21, and he is expected to be out until the All-Star break.

RHP John Smoltz (right shoulder surgery in June 2008) went on the 15-day disabled list retroactive to March 27. He is hoping to pitch for the Red Sox in June despite a setback in late April.

RHP Miguel Gonzalez (sore right elbow) went on the 15-day disabled list retroactive to March 27, and he was transferred to the 60-day DL on April 14.

ROTATION:

RHP Josh Beckett

LHP Jon Lester

RHP Tim Wakefield

RHP Brad Penny

RHP Justin Masterson

BULLPEN:

RHP Jonathan Papelbon (closer)

LHP Hideki Okajima

RHP Ramon Ramirez

RHP Manny Delcarmen

RHP Takashi Saito

LHP Javier Lopez

LHP Hunter Jones

CATCHERS:

Jason Varitek

George Kottaras

INFIELDERS:

1B Kevin Youkilis

2B Dustin Pedroia

SS Nick Green

3B Mike Lowell

DH David Ortiz

SS Julio Lugo

OUTFIELDERS:

LF Jason Bay

CF Jacoby Ellsbury

RF J.D. Drew

OF Jeff Bailey

OF Jonathan Van Every