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08/14/08 8:20 PM ET

Rowand exits with back tightness

Center fielder hopes to return to Giants lineup on Friday

HOUSTON -- Giants center fielder Aaron Rowand left Thursday's game against the Astros in the second inning with tightness in his lower back, but he hopes to rejoin the lineup Friday.

Rowand said he felt much better after undergoing treatment, which he intends to continue Friday. Head athletic trainer Dave Groeschner ordered Rowand to avoid any sudden movement until he reports to Turner Field for the opener of San Francisco's four-game series against Atlanta.

Rowand insisted that he has never experienced any back problems.

"But I aggravated it pretty good today," he said.

Rowand felt fine until he began stretching about a half-hour before the game, when he said he aggravated his sciatic nerve. Pain shot down the back of his right leg.

"My ankle was throbbing from it," Rowand said.

The discomfort continued as Rowand flied out to right field in the first inning. He caught Lance Berkman's routine fly ball to end the inning's bottom half, but Fred Lewis replaced Rowand in center field when the Astros batted in the second.

Rowand shares the team lead in games played, 115, with Randy Winn. Known as one of the toughest players in the Major Leagues, Rowand missed four of San Francisco's first 13 games with a fractured rib -- which he wouldn't publicly acknowledge for weeks -- but has missed only one game (June 7 at Washington) since.

Rowand's batting .286 with a team-high 11 home runs and 62 RBIs, second on the club to Bengie Molina's 66.

Chris Haft is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.