CHICAGO -- With the ball jumping out of Wrigley Field, Pirates manager Clint Hurdle was in search of a reliever who could keep the ball down and help hold a big early lead.
Hurdle was never able to find that reliever.
Anthony Rizzo hit two homers and drove in six runs to lift the Chicago Cubs to a 13-9 victory over Pittsburgh on Sunday.
Pedro Alvarez hit two homers and drove in five runs for the Pirates, who lost for the 12th time in 15 games. Pittsburgh came into play Sunday two games behind the Los Angeles Dodgers and St. Louis Cardinals for the second wild card.
Staked to a 6-1 lead, the Pirates were unable to hold off the Cubs, who have taken five of the last six against Pittsburgh.
Rod Barajas homered for Pittsburgh, and Joe Mather hit a solo shot for the Cubs.
Rizzo hit a two-run shot in a four-run fifth inning, then capped a five-run sixth with his first career grand slam off Jared Hughes (2-2) to put the Cubs up 10-9 and send the home crowd into a frenzy.
Leading 9-5, Hurdle went with sinkerballer Rick van den Hurk, who was unable to retire the three batters he faced before Hughes gave up the grand slam.
"I wanted to bring in the sinker guys in from that point on to try to hold (the lead). I chose van den Hurk. It didn't work," Hurdle said.
Hurdle doesn't believe fatigue is an excuse for his bullpen's struggles.
"I have had people say it's because they are tired, but well sinker guys usually sink it better and throw it better when they are being used more. At least that's my experience," he said. "We are just not getting the job done."
The six RBIs are a career-high, and it was also the 23-year-old's first multihomer game.
"I don't think it tops the walkoff, but it was a great game. Well-fought by all (of us). It was a good game and we kept fighting the last couple of days and showing some resilience," Rizzo said.
David DeJesus had a pinch-hit, two-run single in a three-run ninth for Chicago.
Alvarez followed Gaby Sanchez's leadoff single in the fifth with an opposite-field shot onto Waveland Avenue to give the Cubs a four-run lead.
After the Cubs rallied to get within one, Alvarez hit another opposite-field shot in the sixth with two on to pad the lead again. It was Alvarez's sixth multihomer game of the season. He passed Andrew McCutchen for the team lead with 29.
The Pirates had a chance to tie it when Starling Marte tripled to lead off the seventh, but Marte was caught in a rundown on a fake to third, throw to first by Cubs reliever Jaye Chapman after Neil Walker and McCutchen failed to get the run in.
"Actually that's a forced balk, break late, try to get the throw to second and try to steal a run at home is what it was," Hurdle said. "And I do believe if Starling could've shown a little more patience I think that play would have worked for us, but in the heat of the moment he fired a little bit early. We were hoping he can get in some kind of rundown. He took the out, I thought there might be a little more fight to see if he can make something happen."
Jeff Beliveau (1-0) allowed Alvarez's second home run, but recorded the final two outs of the sixth to earn his first career win.
"He can shrink some ballparks. He did it again today," Hurdle said.
Barajas homered on an 0-2 pitch with a man on and the pitcher on deck in the second inning to reach double-digits for the year.
McCutchen had an RBI single in the second and reached base four times. He has reached safely in nine of his last 11 plate appearances this series.
Pirates starter Jeff Locke was backed by a consistent flow of Pittsburgh offence, but couldn't get through the fifth inning to earn his first big league victory.
"It's tough to pitch when you get behind those guys," Locke said. "I got behind Rizzo 2-0 and you are forced to throw them a strike. The ball was supposed to be down and away and it wasn't down."
The 24-year-old Locke was staked to a 6-1 lead until things fell apart in a four-run fifth.
Mather's one-out solo homer started a string of four straight hits for the Cubs, which included Rizzo's two-run shot.
Cubs starter Chris Volstad gave up six runs and 10 hits in 4 2-3 innings. He walked four and struck out three.
Notes: Hurdle removed RHP James McDonald from the starting rotation due to a poor second half. RHP Kyle McPherson will take McDonald's turn in the rotation Wednesday against Milwaukee. McDonald is 3-5 with a 7.08 ERA since the All-Star break. ... Chicago sends LHP Travis Wood (6-11, 4.23 ERA) to the mound in the series finale Monday against Pittsburgh's RHP Kevin Correia (10-9, 4.29).