Webb was removed from Saturday's game against Colorado due to back/shoulder tightness, Justice delos Santos of The San Jose Mercury News reports.
Webb needed just 80 pitches to make it through six innings Saturday, during which he gave up one run on four hits and zero walks while punching out seven batters. However, he began to feel tightness around his shoulder after getting struck by a comebacker in the fifth inning, so the Giants took him out of the game as a precaution. He's tentatively scheduled to make his next start in Boston next week, but the team will likely monitor his injury over the next few days before confirming his availability.