SCOTTSDALE, Ariz. -- Under the current circumstances, Dave Roberts appears destined to open the season as the Giants' fifth outfielder and play sporadically.

The 10-year veteran isn't ignoring the facts. But nor will he passively resign himself to his fate.

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"It's been a long time since I've been in that role," Roberts said Wednesday before the Giants' first full-squad workout. "But a lot of things can happen before Opening Day. Things have a tendency to change day-to-day. I think if I'm healthy, I can help this ballclub. That's one thing I do know."

A left knee injury limited Roberts, 36, to 52 games last year. He hit .224, his second-lowest average in any season. Roberts, San Francisco's Opening Day left fielder, surrendered his regular's status to Fred Lewis, who's expected to retain that perch this season.

Known as one of baseball's most genial players, Roberts refused to complain. When he discussed his role late in the offseason with Bruce Bochy, Roberts said that he told the manager, "I'll do anything I can to help this team win." Bochy said that reserves such as Roberts "play a major role in determining the success of your season."

Should the Giants open the season with 12 pitchers and three catchers (including Pablo Sandoval), Bochy might be forced to keep only four outfielders -- which would jeopardize Roberts' roster status. Asked whether he could issue an ironclad, 100 percent guarantee that Roberts will be on the Opening Day squad, Bochy replied, "I can't put that number on anything."

Overall, the workout was pleasantly uneventful.

"Everybody showed up in great shape," Bochy said. "That's always very helpful as you go through drills."

Lewis reported that his right foot, which required offseason surgery for removal of a bunion, started bothering him late in the workout. Nevertheless, Lewis pumped four home runs to right field in his final two rounds of batting practice.

"It's getting better," Lewis said. "This week has been the best [it has felt] all spring and last season."

Said Bochy, "There's plenty of time for him to get into the shape he needs to be in."

A tight left hamstring restricted outfielder Nate Schierholtz's activity, but the injury wasn't considered serious.