Carl Crawford will be evaluated after straining his left hamstring in the first inning of the Boston Red Sox's 10-4 win over the Milwaukee Brewers on Friday night.

Crawford left the game after being hurt while reaching first base on an infield single just ahead of the throw from third baseman Casey McGehee. Boston manager Terry Francona and a trainer went out to check on the speedy left fielder, who held the back of his left leg above the knee.

An MRI taken during the game showed a Grade I strain, the least serious kind, Francona said. It was unclear how much time Crawford, who has played 67 of the team's 69 games, would miss.

There will be additional conversations with Crawford and medical personnel to "see what we need to do," Francona said.

He said he thought Crawford was hurt "when he kind of lurched for the bag at the end there. I didn't ask him. He wasn't feeling too good."

Darnell McDonald pinch ran and took second on a walk to Marco Scutaro that loaded the bases. But J.D. Drew grounded out, ending the inning with the score tied at 2. McDonald stayed in the game in left field.

Crawford, who got off to a very slow start in his first season with Boston, is batting .243 with six homers, 31 RBIs and eight stolen bases.

Red Sox third baseman Kevin Youkilis also left, because of a stomach illness and was replaced by Drew Sutton in the top of the fifth.

"He didn't feel too well," Francona said.