Gorkys Hernandez went 3-for-5 with two runs scored out of the leadoff spot for San Francisco while starter Chris Stratton (6-3) got the win. Stratton lasted five innings, yielding four hits and three runs with three walks and six strikeouts.

Jose Quintana (5-4) absorbed the loss, allowing five hits and four runs over 4 1/3 innings. He walked two and fanned six.

Coming off a 6-2 win Friday in the series opener, the Cubs got off to a quick start. They initiated scoring in the second when Jason Heyward simply stood at home plate and kept his bat stationary while four straight pitches missed the strike zone, sending Willson Contreras home.

Chicago made it 2-0 in the third when Stratton left a changeup down and in, the nitro zone for Kyle Schwarber. He drilled it over the wall in right-center, his ninth home run of the year.

Crawford evened the score an inning later on one swing. He drove a 91 mph fastball from Quintana the opposite way to left-center with Mac Williamson aboard for his sixth homer of the season.

Javier Baez crushed a high, inside slider on Stratton's first pitch to him in the bottom of the fourth, launching his 12th homer of the year to left and restoring a one-run edge for the Cubs.

Quintana couldn't hold that lead, either. The Giants took the lead for good in the fifth. Andrew McCutchen tied the score when he laced an RBI double to center that plated Hernandez, and Belt snapped the deadlock when he singled to left to score McCutchen.

Belt added a sacrifice fly in the seventh for a 5-3 advantage. Anthony Rizzo drew Chicago within a run in the bottom of the eighth by slicing an RBI single to left, plating Schwarber.

Hunter Strickland protected the one-run edge in the ninth, earning his 10th save.

--Field Level Media