NEW YORK -- Few managers in baseball are more aware of the game's unpredictable whims than Pittsburgh Pirates skipper Clint Hurdle, who reached the major leagues and made the cover of Sports Illustrated at age 20 but played just 515 big league games, none after his 30th birthday.

But even Hurdle had to marvel a bit at what he saw Friday night, when rookie catcher Elias Diaz was inserted into the lineup half an hour before game time and racked up six RBIs to lead the Pirates to a wild 12-7 win over the New York Mets at Citi Field.

"It's a great game that we've got the opportunity to play," Hurdle said. "The storylines make themselves up."

Diaz was pressed into duty when starting catcher Francisco Cervelli was scratched because of illness. The 26-year-old backup, who entered Friday with two hits and one RBI in 18 big league at-bats dating to 2015, hit a three-run double in the fourth inning to give the Pirates a 4-2 lead.

The Mets scored five times in the bottom of the fifth, but Diaz fueled a seven-run top of the sixth by crushing a go-ahead three-run homer.

"What a game," said Pirates starter Gerrit Cole, who gave up all seven Mets runs, eight hits and two walks while striking out six in five innings but was credited with the win thanks to the sixth-inning outburst. "I'm sure it's one he'll remember for a long time."

It's one Diaz has waited to enjoy for a long time. He signed with Pittsburgh in 2008 and was in line to back up Cervelli last season before suffering an elbow injury in spring training.

Diaz ended up enduring two stints on the 60-day disabled list -- including one for a season-ending leg infection in September -- and opened this season with Triple-A Indianapolis.

"He hasn't been healthy is the biggest thing," Hurdle said. "This guy has put himself in position way before this to help out, but the health has always been somewhat of an issue."

Now, Diaz was the one stepping in for banged-up Pirates catchers. Diaz, who spent a week with the major league club in early May, was recalled Tuesday, when backup Chris Stewart went on the 10-day disabled list because of a hamstring injury.

"I'm very grateful -- yes, I have gone through a lot," Diaz said through an interpreter. "I've kept my head up, I've kept working hard. I'm just glad to be here. This is my career."

Josh Bell led off the sixth with a homer to pull the Pirates (25-30) within 7-5. Mets starter Matt Harvey then plunked Andrew McCutchen before being pulled for Paul Sewald, who gave up a single to Jordy Mercer before surrendering Diaz's homer.

Sewald (0-1) struck out Max Moroff — pinch-hitting for Cole — before allowing the final six batters he faced to reach base. Josh Harrison (double) and Bell (bases-loaded walk) collected RBIs before McCutchen hit a sacrifice fly off Neil Ramirez.

Sewald was charged with five runs after giving up just three runs in his previous 20 innings.

"One of those days," Sewald said.

Mets manager Terry Collins said he stayed with Sewald because he only had four available relievers.

"At that time when we brought him in, we said, 'You've got to get us through this inning,'" Collins said. "And he couldn't do it."

Harrison added a homer leading off the eighth and finished with three hits for the Pirates, who snapped a two-game losing streak. Bell and Mercer had two hits apiece.

Four relievers combined to limit the Mets to one hit in the final four innings.

Lucas Duda hit two homers -- a two-run shot that gave the Mets a 2-1 lead in the second and a solo blast to cap the fifth-inning outburst -- for New York (23-30), which has lost three straight.

Michael Conforto laced a two-run homer in the fifth, when Neil Walker delivered an RBI triple and scored on a wild pitch. Travis d'Arnaud finished with two hits.

Harvey gave up six runs, five hits and four walks while striking out five in five-plus innings.

NOTES: The Pirates recalled INFs Phil Gosselin and Max Moroff from Triple-A Indianapolis, optioned INF Gift Ngoepe to Indianapolis and designated for assignment INF Alen Hanson. ... Pirates RHP Jameson Taillon (testicular cancer) allowed an unearned run in five innings for Triple-A Indianapolis. It was the second rehab start for Taillon, who underwent surgery May 8. ... Mets RHP Seth Lugo (elbow) and LHP Steven Matz (elbow) are both scheduled to make rehab starts -- Lugo for Double-A Binghamton, Matz for Triple-A Las Vegas -- on Saturday. ... Mets 3B David Wright and former Mets LHP John Franco were among the team personnel present in Little Falls, N.J., where a Little League park was dedicated to late Mets public relations executive Shannon Dalton Forde, who died of breast cancer in March 2015.