PITTSBURGH -- Former New York Mets left-hander Jonathon Niese limited his former team to four hits in seven shutout innings, Jordy Mercer hit his first homer in his home park in 22 months and the Pittsburgh Pirates beat New York 3-1 on Tuesday in the first game of a doubleheader.

Niese (6-2), traded by the Mets to Pittsburgh six months ago for second baseman Neil Walker, was in control from the start -- allowing multiple base runners in an inning only once.

Niese struck out two, walked two and got 14 outs on ground balls in outdueling Mets left-hander Steven Matz (7-2), who lost for only the second time in 15 career starts.

Josh Harrison had a triple among his three hits and scored twice for the Pirates, with David Freese and Andrew McCutchen contributing run-scoring singles off Matz.

The Mets, losing their eighth in a row to the Pirates dating to June 29, 2014, loaded the bases down 1-0 in the fourth on singles by Walker and Wilmer Flores and James Loney's walk. But Niese, facing his former club for the first time, struck out Michael Conforto to end the threat.

Matz hit his first major league triple with one out in the fifth, but Niese -- winning his third in a row -- got Curtis Granderson and Asdrubal Cabrera to ground out.

Matz had won seven in a row since a 10-3 loss to Miami on April 11 and was 11-1 in his career dating to his debut last season. But he gave up eight hits and walked two despite striking out eight and was lifted after five innings.

The Pirates jumped on Matz for Harrison's leadoff triple and Freese's RBI single in the first. Harrison then singled, stole second and scored on McCutchen's single in the fifth.

Mercer hit his second home run of the season -- and his first at PNC Park since Aug. 31, 2014 -- in the sixth off former Pirates reliever Antonio Bastardo.

Granderson, previously 5-for-74 (.068) in his career against the Pirates, supplied the only Mets run with a solo homer -- his 10th home run of the year -- agains treliever Neftali Feliz in the eighth. Mark Melancon pitched the ninth for his 18th save in 19 opportunities.

Pirates left fielder Starling Marte left the game in the sixth because of what the team said was left ankle discomfort. He was being checked as the game ended.

The traditional doubleheader -- the second game was to start a half-hour after the first game ended, with fans required to buy only one ticket -- was necessitated by a Monday night rainout.

NOTES: RHP Jameson Taillon, the Pirates’ top pitching prospect, is being called up from Triple-A Indianapolis to make his major league debut Wednesday against the New York Mets. He’ll face RHP Noah Syndergaard (6-2). The 24-year-old Taillon was 4-2 with a 2.04 ERA in Triple-A. ... Pirates LHP Francisco Liriano (4-5) was scheduled to start against the Mets, but was bumped back to Saturday to face the Cardinals. RHP Gerrit Cole (5-4) goes Friday, after LHP Jeff Locke (5-3) pitches a makeup game Thursday at Colorado. ... Because of the Monday rainout, Mets RHP Logan Verrett (3-3, 3.41 ERA) will start either Friday or Saturday in Milwaukee. ... Taillon will be the first high school pitcher drafted under Pirates GM Neal Huntington’s tenure to pitch in the majors. Taillon posted this message on Twitter: “This journey is still just beginning.” However, Pirates manager Clint Hurdle is not committing to more than one start for Taillon at the moment. ... The Pirates called up RHP Wilfredo Boscan to be their 26th man in the second game of the doubleheader. The Mets added INF Eric Campbell.