A classic pitcher's duel ending with a walk-off Rockies victory Saturday afternoon at Coors Field. Rookie third baseman Nolan Arenado drove a two-out, 2-2 pitch up the middle for a single off reliever Jeremy Affeldt to score Josh Rutledge in the ninth inning, lifting Colorado to a 2-1 victory over the Giants. "I was just looking for something up, because he works low and he's got a got a pretty good curveball," Arenado said. "He hung a splitty and I was fortunate to put a good swing on it." Said manager Walt Weiss: "Nolan is one of those guys who likes to be in the box with the game on the line, and he likes the ball hit to him. You don't see that very often with young players. He's able to slow the game down and he wants to be the guy." The rally began when veteran Todd Helton drew a two-out walk. Rutledge entered to run for Helton. Rutledge stole second, setting the table for Arenado's second walk-off hit of the season. He hit a walkoff homer against the Padres on June 7 at Coors Field. Starters Jorge De La Rosa and Matt Cain were masterful. De La Rosa, the Rockies' lefty, allowed one run on six hits over six innings before leaving the game with a bruised left thumb. It's something that has bothered him since a June 17 start at Toronto. "It hurt (beginning with) my first pitch in the bullpen today, but I can still pitch," De La Rosa said, adding that he's sure he will make his next scheduled start. De La Rosa made a quick exit before the seventh inning began. Weiss and trainer Keith Dugger visited De La Rosa on the mound and checked out his thumb. Though De La Rosa had thrown only 86 pitches, he was replaced by reliever Wilton Lopez with the game knotted 1-1.