Cubs 8, White Sox 2: Alfonso Soriano homered among three hits and Luis Valbuena hit a tiebreaking two-run double in the five-run eighth inning to lift the visiting Cubs to a season sweep of their crosstown rivals.

Matt Garza (5-1) won his fourth straight start, limiting the White Sox to two runs - one earned - over seven innings as the Cubs claimed the last of four meetings to finish the first sweep in the Crosstown Cup since 1998.

The Cubs put Garza in line for the win with the eighth-inning rally, as Valbuena roped a double to left-center to make it 4-2, Dave Sappelt added a run-scoring single and Cody Ransom tacked on a two-run single. Sappelt recorded his first career four-hit game and Soriano scored four runs.

Valbuena gave the Cubs a 1-0 lead with a sacrifice fly in the second before rookie Josh Phegley tied it with a blast to left-center in the third. Soriano's solo shot put the Cubs on top in the sixth, but Gordon Beckham tied it when he swiped home on a delayed double steal in the bottom of the inning.

White Sox starter Hector Santiago allowed two runs on five hits in 5 1/3 innings. Matt Thornton (0-3) took the loss, as he was charged with three runs while recording only one out in the eighth.

GAME NOTEBOOK: The start of the game was delayed 29 minutes because of rain. … Phegley has hit a home run in two of his first three major-league games and has hit safely in all three. He has hit homers in back-to-back games earlier in his career than any White Sox player since Magglio Ordonez did it in his second and third games in 1997. … Soriano stole his ninth and 10th bases of the season, giving him double digits for the first time since 2008. Soriano totaled eight stolen bases over the past two seasons combined.