Rapid Reaction: Giants 13, Cubs 7

CHICAGO -- The Cubs lost first game of a split doubleheader to the Giants 13-7.

How it happened: Cubs starting pitcher Doug Davis allowed 15 baserunners in 4 1/3 innings, giving up 10 earned runs on 12 hits and three walks. Davis fell to 1-7 with a 6.50 ERA. Carlos Pena continued his hot slugging with his seventh home run in 12 games. Pena has 17 homers on the season. He’s tied with Prince Fielder for the most home runs in May with 10.

What it means: The Cubs’ bullpen will be tested after going 4 2/3 innings in the first game and missing Rodrigo Lopez in the second game, because Lopez is the emergency starting pitcher. Manager Mike Quade said Lopez will most likely be held to 80 pitches.

Outside the box: Two rehabbing Cubs players at Triple-A Iowa, Marlon Byrd and Darwin Barney, enjoyed good games on Tuesday. Byrd homered and doubled in his second minor league game. Barney went 2-for-3 with a double. Quade said Barney will return to the Cubs on Wednesday and will be in the lineup against the Giants’ Tim Lincecum.

Next: Game 2 of the doubleheader: Rodrigo Lopez (0-1) vs. Barry Zito (0-1).