Fred Lewis was in the San Francisco Giants' lineup last night as the starting left fielder and leadoff hitter.

His ability to stay there — for opening day and beyond — will hinge in part on whether he can improve as much with the glove as he has with the bat.

Manager Bruce Bochy acknowledged as much before the Giants faced the Seattle Mariners in an exhibition game at AT&T Park.

"Defense is an area he can improve on and needs to improve on," Bochy said of Lewis. "But he's an exciting player."

Lewis entered play Thursday hitting .292 with two doubles, four triples and a home run in 65 at-bats this spring.

His energetic play, coupled with Dave Roberts' knee injury, have kept open the possibility that Lewis will be the starter when the Giants open the regular season Monday against the Los Angeles Dodgers.

Bochy said he does not yet know whether Roberts or second baseman Ray Durham will be healthy enough for Game 1.

That leaves Lewis with a chance for an extended audition — and for some more improvement in the field.

Lewis focused on football and basketball growing up, so some of his baseball skills remain raw. Though speedy, he has been caught stealing six times in eight attempts, including a pickoff by Mariners right-hander R.A. Dickey in the first inning yesterday.

Lewis sometimes takes shaky routes to the ball. His throwing arm won't make anyone forget Roberto Clemente.

Still, Bochy is optimistic about the long term.

"There's no reason he can't be one of the better outfielders in this league with his speed and the jumps he gets on the ball," he said.