Jay Bruce stepped up and took advantage, breaking a tie with Conforto for the team lead in RBIs by driving in two as New York rolled to a 7-2 series-clinching victory at PNC Park.
Bruce finished the night 3-for-5 with two doubles and a run. He now has 34 RBIs on the season, pulling into a tie for the 10th in the National League.
Collins said the decision was more about a rest day for Conforto, who had played 44 of the Mets' first 47 games, than it was about his recent performance.
"I wanted him to play tomorrow at home, so we had a choice of either tonight or tomorrow," Collins said.
Bruce's breakout was part of a big turnaround for the New York offense. On Saturday, the Mets left five runners in scoring position in the first four innings, instead relying on the long ball as they staked an early 4-2 lead. However, they couldn't hold on to it late and lost 5-4 in 10 innings.
On Sunday, the Mets didn't provide as much power, but they pushed two runners across in the fourth inning and three in the fifth to build another sizable early lead. Nine different Mets had hits on the way to the rout, with Curtis Granderson going 3-for-5.
In the fifth, pitcher Matt Harvey got it started with a single back through the legs of his mound opponent Tyler Glasnow. Granderson drove him in with a double. A single and a stolen base by Jose Reyes put two men in scoring position for Bruce, who brought them in with a liner to right over a drawn-in infield.
Harvey (4-3) won back-to-back starts for the second time this season and the first time since April 6 and 11 -- his first two starts of the season. He pitched six innings, which was his longest outing since April 21, and scattered six hits while giving up just one run. He struck out four and issued two walks.
"It's a good feeling when you can reach back and get that strikeout when you need it," Harvey said. "That hasn't been the case very often this year."
The first five New York runs came off Glasnow (2-4), who gave up only one hit through the first three innings, but it was all downhill after that. He ended up allowing eight hits in five innings. He struck out three and didn't walk a batter.
"I kind of just lost the feel for things," Glasnow said. "The curveball flattened out. The changeup flattened out. I lost the angle on my fastball. ... It's good to know that when I have my stuff, it's hard to hit. It's a little frustrating knowing that from one inning to the next, it can turn like that."
The Mets added two runs off reliever Jhan Marinez. Granderson drove in Cabrera with an RBI single in the sixth, and Lucas Duda hit a solo home run in the seventh.
Both Pirates runs were scored by Gregory Polanco. He hit a solo home run in the second and singled and scored on David Freese's RBI double in the eighth. Polanco finished 2-for-4. Since returning from the disabled list on May 26, he is 5-for-13 (.385) with two home runs.
Paul Sewald and Neil Ramirez combined to throw three innings of one-run ball in relief of Harvey.
NOTES: Pirates RHP Jameson Taillon threw 47 pitches in a three-inning rehab start for Double-A Altoona. It was his first appearance since recovering from surgery to treat testicular cancer on May 8. Taillon is expected to rejoin the team in Pittsburgh and throw a bullpen session on Tuesday. He will make at least one more rehab start before rejoining the rotation. ... Mets LHP Stephen Matz (sprained flexor tendon) threw five perfect innings in a rehab start for Triple-A Las Vegas. ... Mets OF Yoenis Cespedes (strained left hamstring) had his second rehab start indefinitely postponed after coming up with soreness in his quad in his first game back with Class A St. Lucie on Friday. ... Mets RHP Seth Lugo made his third rehab start on the way back from a partial tear of his ulnar collateral ligament. He threw six innings for Double-A Binghamton, allowing three runs on eight hits with seven strikeouts.