Edgar Renteria's seventh inning walk-off grand slam put the Giants ahead of the Rockies yesterday, 6-5, but it wasn't enough to secure the victory as the team's subsequent celebratory exit from the field caused them to lose via forfeit. "I thought you could hit a walk-off home run at any point in the game as long as it was dramatic," said Giants manager Bruce Bochy. "And that one was as dramatic as they come. The league office needs to clarify the rules." Rockies reliever Rafael Betancourt, who surrendered Renteria's grand slam, took the win while seeing his ERA go up 19 points.