Pittsburgh stranded 10 runners through six innings before sending 10 batters to the plate against a trio of pitchers in the seventh. Pittsburgh scored its first three runs via a bases-loaded walk, a bases-loaded hit batter and a bases-loaded passed ball before Delay split the right-centerfield gap off rookie right-hander Grant Hartwig.
"Get him up and then find something out over the plate I could hit in the air," Delay said. "Really just trying to get that run in. The situational hitting approach. Luckily, it found a gap."
One out later, Bryan Reynolds hit a run-scoring triple.
"I think one of the things, when you leave guys on base like that, you work through pitchers and we did a good job of that," Pirates manager Derek Shelton said. "We missed some opportunities early, but we did a nice job staying patient."
Colin Selby (1-0), making his fourth big league appearance, entered a 1-1 game in the sixth and got the win despite allowing back-to-back homers - a two-run pinch-hit shot by DJ Stewart followed by Jonathan Arauz's second homer in as many games.
Selby, a 16th-round pick in the 2018 amateur draft from Division III Randolph Macon College, made 116 appearances in the minors before being recalled by the Pirates on Aug. 8.
"Came in a big situation - I know the second inning didn't go the way he wanted it to, but came in in probably the biggest situation against one of the better hitters in the National League and did a good job," Shelton said. "So I'm really happy for him. It's nice to get that checked off."
David Bednar tossed a scoreless ninth for his 25th save in 28 chances.
Liover Peguero homered in the second for the Pirates, who went 3 for 13 with runners in scoring position and left a season-high 13 on base.
The homer was the fifth in 22 big league games for Peguero, who had 13 homers in 76 games between Double-A Altoona and Triple-A Indianapolis before being promoted to the majors on July 17.
"All I'm trying to do right now is swing at the pitches that are good for me to hit," Peguero said.
New York pitchers walked 10, their most since 2020. The Mets have lost 12 of 17 since starting their selloff late last month.
"I'm surprised that they didn't score more runs (with) that many people out there," Mets manager Buck Showalter said.
Mets outfielder Brandon Nimmo tied his career high of 17 homers with a leadoff drive in the first.
Jose Butto (0-2) allowed three runs, two hits and three walks in 2 2/3 innings.
Bailey Falter gave up one run and struck out five in 5 1/3 innings for the Pirates. He is 0-7 in 10 starts and one relief appearance this year.
Mets starter David Peterson allowed one run and walked a career-high six in 3 2/3 innings.
Pittsburgh recalled right-hander Yohan Ramirez from Indianapolis and optioned right-hander Quinn Priester to the Triple-A farm team. The 22-year-old Priester was the loser Monday and is 2-2 with a 9.10 ERA in six starts.
"There's very few guys that come to the big leagues at 22 and stay and don't go back," Shelton said. "He's part of our long-term success here, but we've just got to get some things kind of tuned up a little bit."
The Mets recalled Butto from Syracuse and optioned Tyson Miller to Triple-A in an exchange of right-handers. Miller won with two scoreless innings in his New York debut Monday.
MOVIN' ON UP
Shelton grinned when asked if he was looking forward to watching footage of Paul Skenes' debut with Class A Bradenton. Skenes, taken first overall in last month's amateur draft, allowed one hit and struck out two in one inning in his second professional appearance Tuesday night.
"I think when we have a guy like that that is a high-profile guy, yeah, it's exciting to be able to see how he executes," Shelton said.
ON THE FARM
New York 3B Brett Baty had a grand slam, double and five RBI against Columbus in his fifth game for Triple-A Syracuse.
Pirates: CF Joshua Palacios (gastrointestinal illness) was lifted for pinch hitter Jack Suwinski in the seventh inning.
Mets: Peterson dodged injury in the third, when Peguero's one-hopper glanced off his glove - which Peterson raised just in time to protect his face - and trickled away for an infield single.
Pirates RHP Johan Oviedo (6-12, 4.42 ERA) opposes Mets RHP Tylor Megill (6-6, 5.64 ERA) in Wednesday afternoon's series finale. Both pitchers gave up six runs in defeats last Friday, when Pittsburgh fell to Cincinnati and New York lost to Atlanta.