Pagan tweaked his hamstring during an inside-the-park walk-off home run against the Colorado Rockies, and was playing in his first game since the injury. The outfielder hit a ground ball to second in the ninth inning, but could not run out the grounder, falling to the ground after limping down the line.
The 31-year-old was attempting to make a comeback without the aid of surgery, which could have sidelined the outfielder for at least a month, per Chris Haft of MLB.com. Pagan believed earlier in the week that he could return to the Giants lineup soon, but the most recent setback makes surgery a strong possibility, Andrew Baggarly of CSN Bay Area notes.
Pagan, who signed a four-year, $40 million contract with San Francisco this offseason, hit .262/.314/.374 in his first 204 plate appearances in 2013. Juan Perez, Andres Torres and Gregor Blanco will continue to rotate in center and left field in Pagan's absence, with Hunter Pence in right.