PITTSBURGH -- As the Pittsburgh Pirates came to the plate in the fourth inning Tuesday, they trailed the Cincinnati Reds by four runs. While right-hander Josh Smith walked five in his first three innings, he also held the Pirates hitless.

Pittsburgh also hadn't led in 30 innings since their victory against the Chicago White Sox on Thursday as the Washington Nationals swept it in the nation's capital over the weekend.

But none of the above caused the Pirates to change their approach.

"We just kept reminding us we didn't need to be in a hurry," Pirates manager Clint Hurdle said. "We wanted to have the best at-bat we could, one pitch at a time."

The stubbornness paid off as Pittsburgh scored seven runs in the fourth inning, which proved all the offense they needed in a 7-6 win over the Reds.

"We needed to shut that inning down and we really couldn't," Cincinnati manager Bryan Price said. "We made some mistakes in that inning that kept it moving and eventually they were able to score enough runs to put us in a hole we couldn't dig out of."

Pittsburgh's offensive explosion was keyed by catcher Francisco Cervelli's game-tying three-run home run and center fielder Andrew McCutchen's two-run blast later that put the Pirates up 7-4.

"We lost three in a row on the road, we were like, 'we're going to win at home,'" McCutchen said. "You lose like we did against the Nationals, you're pretty amped up after that off day to be back in front of your home crowd and ready to go."

The seven-run fourth set a season-high for runs scored in an inning.

Neither team's starter lasted past the fourth inning.

Pirates right-hander Rob Scahill worked two-thirds of an inning and got the victory after he came on in relief of left-hander Jeff Locke. Scahill (2-3) was charged for one run and two hits.

Cincinnati right-hander Pedro Villarreal replaced Reds right-hander Josh Smith in the fourth and took the loss. Villarreal (0-2) gave up three unearned runs on two hits.

Smith made his major league debut but both he and his manager noted he was trying to pitch a little too perfect in his first start.

"Just nerves and trying to be too fine," Smith said. "I didn't really get tired or anything, I just didn't make enough good pitches."

Cincinnati scored before Locke recorded an out. The Reds led off with four consecutive singles by second baseman Brandon Phillips, first baseman Joey Votto, third baseman Todd Frazier and right fielder Jay Bruce.

Phillips scored on Bruce's single for a 1-0 lead.

Two more runs crossed when shortstop Eugenio Suarez hit a grounder to Pittsburgh first baseman Pedro Alvarez, who threw to shortstop Jordy Mercer for the force-out on Marlon Byrd. But Mercer's throw was behind Locke, covering first on the play, and Bruce scored after Frazier.

Bruce drove in his second run of the game with the bases loaded in the fourth. He grounded a slow roller to first that allowed center fielder Billy Hamilton to score from third and put Cincinnati up 4-0.

The Reds scored six runs on 14 hits Tuesday but fell one shy. They left 12 men on base and hit 4-for-17 with runners in scoring position.

"I thought we did a good job getting guys on base and creating scoring opportunities," Price said. "We just weren't able to deliver the big blow that would've us the separation we could've covered with the bullpen."

Cincinnati got a run back after the Pirates took the lead with the fourth-inning explosion when catcher Tucker Barnhart led off the fifth with a double and scored on Hamilton's sacrifice fly.

Bruce cut the Pirates' lead to one run with his 12th home run of the season, a solo shot in the sixth inning.

But Pittsburgh left fielder Starling Marte prevented the tying run from scoring in the seventh when he dove headfirst to snatch a low line drive off the bat of Frazier. The catch ended the inning with center fielder Billy Hamilton on third.

Right-hander Mark Melancon struck out the side in the ninth to collect his 24th save.

NOTES: Pittsburgh 2B Neil Walker returned to the starting lineup for the first time since June 16 after missing four of the team's last five games with a stomach ailment. ... Cincinnati RHP Johnny Cueto's scheduled start on Tuesday was pushed back to Friday. ... Reds RHP Josh Smith made his major league debut on Tuesday.