Steven Matz was doing his part Saturday night, going toe-to-toe with Phillies ace Aaron Nola in an old-fashioned pitchers’ duel through the first four innings.

By the end of the fifth, the game had become a lopsided affair. The Phillies broke it open with a five-run frame and never looked back, handing the Mets a 6-2 loss at Citizens Bank Park.

• Box score

“It's really, really frustrating for me,” said Matz, who allowed six runs on five hits and three walks over 4 1/3 innings. “I’m trying to stay positive, trying to take the positives out of it. I just have to execute better, give the team a better chance to win. It's unacceptable.”

Nola struck out eight over seven scoreless innings, though the Mets avoided being shut out for the second time this season thanks to Dominic Smith’s two-run homer in the ninth against Ramón Rosso.

It marked the second straight setback for the Mets, who will try to avoid a three-game sweep on Sunday when they face Zack Wheeler for the first time since he signed with the Phillies last winter.

Matz had struggled badly during his first two starts in August, allowing 13 earned runs over just 7 1/3 innings. Those performances prompted talk of pitch-tipping from Matz himself, something manager Luis Rojas and pitching coach Jeremy Hefner discussed in recent days.

Whatever adjustments Matz made, they seemed to be working in the early innings. Focusing on slowing down his tempo, Matz was pleased with his fastball command, throwing it in, throwing it down and away, working his changeup in to keep the Phillies off balance.

Jean Segura gave the Phillies a lead with a solo homer in the second, the only hit Matz allowed through four innings.

“I felt really good,” Matz said. “I felt like I was commanding the ball really well.”

Nola flirted with danger in the first and third, getting a big strikeout each time as he stranded three runners in scoring position. His inning-ending punchout of Smith in the third sparked a dominant run for Nola, who retired 13 Mets in a row from that point forward.

“Some at-bats with runners in scoring position, especially being in the middle of the lineup, I need to be able to get that job done,” said Smith, who has gone deep in four straight games thanks to his late homer. “We had a big situation, had Nola on the ropes, and same thing today; I have to stay locked in, stay in my zone and don't chase those pitches.”

Matz, whose propensity for giving up big innings has been a pattern throughout his career, was not that fortunate. Two singles and a walk loaded the bases for the Phillies with nobody out in the fifth. Scott Kingery lined out to right field, then Matz walked Andrew McCutchen to force in the game’s second run.

A visit from Hefner didn’t have much of an impact; Rhys Hoskins drilled Matz’s next pitch to right-center for a bases-clearing double that pushed the Phillies’ lead to 5-0. Bryce Harper followed with another double, lengthening the lead to six on Matz’s final pitch.

“It's very difficult,” Matz said. “Ultimately I’ve got to just try to find stuff that I did well and just build off that.”

Whether he’ll try to do so as a starter or a reliever remains to be seen. With an 0-4 record and 9.00 ERA in five starts, Matz hasn’t done much to help the Mets win this season. The worst of it has come in August, posting a 14.66 ERA in three losses this month.

Rojas said he and his coaching staff would discuss the situation like “we typically do when players have tough nights like this.” When the manager was asked if Matz would remain in the rotation -- a group already dealing with its share of injuries -- Rojas declined to commit one way or another.

“That's something we really don't want to get into right now,” Rojas said. “We don't want to start talking about it right now. We really want to slow things down now and be able to talk about what's going on. We just finished this game and it was just another tough outing for him.”