Rapid Reaction: Cubs 6, Giants 4

CHICAGO -- The Chicago Cubs jumped on the first-place San Francisco Giants early, earning a 6-4 victory Friday in the series opener.

How it happened: After scoring nine runs over the final four innings against the Milwaukee Brewers Thursday, the Cubs picked up right where they left off against the Giants with five runs in the first three innings. Alfonso Soriano and Anthony Rizzo hit home runs and Chris Volstad won for the second consecutive start. Carlos Marmol earned his 17th save and 16th consecutive. The first-place Giants had a quick turnaround Friday after playing a night game at Houston on Thursday.

What it means: Volstad is now on a streak of a different kind. After not posting a victory for 24 consecutive starts, four short of the major league record, the tall right-hander has now won two consecutive outings. He gave up two runs over 5 2/3 innings to the Giants on Friday after pitching 6 2/3 scoreless innings Sunday against the Rockies. Volstad has actually delivered three starts of two runs or less this month and four of three runs or less.

Outside the box: Rizzo had to wait for a replay to confirm it, but ultimately he walked away Friday with his first home run since Aug. 5 at Los Angeles. Rizzo’s opposite-field shot into the basket in left-center bounced back on the field quickly, confusing umpires. Rizzo ended the month with just six extra-base hits and three of those came in the past two days. The home run was his 10th of the year.

Off beat: In the previous series against the Brewers, the Cubs allowed a base runner to advance from first base to home because of defensive miscues. On Friday, the Cubs did one better. Welington Castillo doubled in a run in the third inning and advanced to third on the throw to the plate. He then finished his tour completely around the bases when catcher Buster Posey couldn’t handle the throw and pitcher Madison Bumgarner failed to back up the play.

Up next: the Cubs will send right-hander Justin Germano (2-4, 5.91 ERA) to the mound Saturday against San Francisco in the second game of the three-game series. The Giants will counter with right-hander Tim Lincecum (7-14, 5.30) in the 12:05 p.m. start from Wrigley Field.