PITTSBURGH -- Travis Snider took a pregame pep talk from his manager to heart. Relaxed and with a clear head, he delivered a crucial sixth-inning home run for the second time in five games.
Garza allowed one hit over five shutout innings in his first outing in 10 months, but the Pirates pounced on a Chicago bullpen that is 10th in the National League in ERA by sending 11 men to the plate in the sixth.
Snider, who homered for the first time in nine months in a win over Milwaukee on Thursday, hit his first career home run with the bases loaded. It was the first Pirates pinch-hit grand slam in five years.
"Tonight was probably the most calm pinch-hit at bat I've had," Snider said. "(Manager Clint) Hurdle gave a good speech before the game just talking about situations that come up, whether it's in the sixth inning, the first inning, eighth inning, ninth inning -- the game's the game. And over-thinking those situations isn't going to make it any easier for you if you don't get a hit. So I just tried to go up there and be patient.
"I got ahead of the count and was able to sit back on a changeup."
Wandy Rodriguez (5-2) allowed three runs on six hits over six innings for the Pirates, who have won nine of 11.
Darwin Barney went 4 for 4 for the Cubs, who have lost three of four.
Snider's second homer was the first pinch-hit grand slam by a Pirates player since Jason Michaels on June 2, 2008, at St. Louis. It came off of Shawn Camp after Hector Rondon and James Russell (1-1) had combined to load the bases. Pedro Alvarez walked to drive in a run.
The Pirates did not have a hit against Garza until Clint Barmes singled to right with one out in the fifth.
Garza had been sidelined since July 21 because of a stress reaction in his right elbow and, later, a strained upper back muscle.
"He was really good," Cubs manager Dale Sveum said. "He had a really good slider. His command, for it being his first time back, was outstanding. Even when he missed, he didn't miss by much. His velocity was good, too, consistently at 93-94. He was just outstanding."
Limited by a pitch count, Garza threw 82 pitches.
"I felt great out there," Garza said. "I had some butterflies and the first couple of innings flew by. I had to kind of stop myself at one point and just slow down but it was fun. It was a long, long time and it's nice to not only come back but pitch well. You don't want to spend that much time working to get back and then pitch poorly."
Or, apparently, to hit poorly either. The lone inning in which Rodriguez allowed a runner to progress past first base was the second, when Barney had an RBI single and Garza hit a two-run double.
Cubs pitchers have 13 RBIs in May -- the most for the franchise in any month since September 1971. They also have a major league leading six doubles.
But after that, Rodriguez retired 13 of the final 15 he faced.
"At the beginning, I didn't have good stuff," Rodriguez said through a translator. "Then I started using the breaking ball and hitting spots and I was successful at that."
The Cubs scored once in the ninth on a single by Starlin Castro, but Jason Grilli stuck out Anthony Rizzo swinging with two on to end the game and earn his majors-leading 18th save. Rizzo finished 0 for 5.
After sitting out Pittsburgh's previous game Sunday due to knee soreness, Andrew McCutchen went 0 for 4. He made two of the Pirates' three outs during the sixth, leaving the bases loaded to end the inning.
To make room for Garza on the roster, the Cubs earlier Tuesday designated RHP Michael Bowden for assignment. Also Tuesday, Chicago claimed RHP Eduardo Sanchez off waivers from the St. Louis Cardinals and assigned him to the Triple-A Iowa Cubs. ... The Pirates reinstated RHP Jose Contreras from the bereavement list before the game and returned RHP Jared Hughes to Triple-A Indianapolis. ... LHP Francisco Liriano will make his third start for the Pirates when the series continues Wednesday. He has faced the Cubs once in his eight-year career. RHP Jeff Samardzija, who has a 0.92 ERA in 39 career innings vs. Pittsburgh, starts for the Cubs.