PITTSBURGH -- Anthony Rizzo started a six-run fifth inning with his 30th homer, and the Chicago Cubs rallied for a 9-6 victory over the Pittsburgh Pirates on Thursday to take three of four games between NL playoff contenders.
The Cubs moved within two games of the wild card leaders. Should the teams end up tied at the end of the regular season, Chicago would have home-field advantage, having won the season series with 10 wins in 16 games.
Pittsburgh trails St. Louis by 4 1/2 games in the NL Central. The Cardinals play a night game against the Brewers at Milwaukee.
Richard allowed two runs in 3 1-3 innings in relief of starter Kyle Hendricks, who gave up four runs on three home runs in three innings. Travis Wood struck out five in two perfect innings for his second save.
Charlie Morton (9-8) lost for the fourth time in five starts as he was rocked for six runs - five earned - and nine hits in four-plus innings.
Polanco hit an RBI single in the seventh and scored on Walker's double to pull the Pirates to 9-6.
The Pirates went ahead 4-3 in the third inning when Polanco led off with his ninth home run and Alvarez hit a two-run shot, his 24th.
The Cubs built 3-0 lead as a first-inning run came home on a double play grounder then Russell and La Stella had RBI doubles in the second.
Snider hit a solo homer in the second, his fourth of the season and first since the Pirates re-signed him last month after he was released by the Baltimore Orioles.
Cubs: RF Jorge Soler was activated from the 15-day disabled list after being out since Aug. 24 with a strained left oblique.
Pirates: Mercer replaced INF Jung Ho Kang in the top of the first inning when the rookie sustained a knee injury as Chris Coughlan slid into him while unsuccessfully attempting to break up a double play. The Pirates did not immediately provide a report on Kang's injury.