Rapid Reaction: Giants 7, Cubs 6

CHICAGO -- Here's a quick look at the Chicago Cubs' 7-6 loss to the defending world champion San Francisco Giants:

How it happened: Starlin Castro's two-out error in the fourth inning opened the floodgates for the Giants as they scored four times after the ground ball got by him. The big blow was a two-run bases loaded double by Pablo Sandoval. It came with the Cubs leading 5-0 as Brent Lillibridge had his first hit as a Cub, a two-out bases-loaded single in the third. After pulling within one in the fourth, the Giants took the lead for good in the fifth as reliever Hisanori Takahashi walked pitcher Ryan Vogelsong with the bases loaded and then gave up a sacrifice fly and two-run single to Ben Crawford. Anthony Rizzo homered for the third time this season but the Cubs managed just one run the rest of the way on a double-play grounder by Welington Castillo in the eighth.

What it means: Starter Scott Feldman didn't pitch great but it's hard to fully judge him -- as a pitcher -- when errors or mental lapses are made behind him or by him. In the same inning Castro made his error Lillibridge decided not to throw a ball to Feldman as he covered first on a ground ball which went wide of Anthony Rizzo. Feldman has been involved in three such issues covering first base this season already, although on that play Lillibridge made the mistake. Infield defense was supposed to be a strength of the Cubs this year -- it's been anything but. The Cubs are now 3-6 on the season.

Key stats: The Cubs have committed the most errors in the majors this season with 10. Castro has three … Nate Schierholtz was 3-4 with a stolen base against his former team, raising his average to .370 … Rizzo has just six hits this season but three have left the park.

What's next: The four-game series with the Giants continues as Carlos Villanueva takes the mound at 1:20 p.m. CT Friday.