PHILADELPHIA — The Mets are giving left-hander David Peterson another start Sunday in the series finale against the Philadelphia Phillies, giving him a chance to return to some normalcy.

It’s been a dismal season for the 30-year-old, but the Mets haven’t exactly made it any easier for him by moving him into and out of the rotation periodically. At one point recently, the Mets didn’t use him for more than a week, then used him behind an opener. The result was one of his worst outings of the season.

Peterson is 3-5 with a 5.91 ERA in 15 games (seven starts), with one save. The Mets felt he was the best option to counter a Philadelphia lineup heavy on left-handed hitters, and cited his history of pitching against the Phillies.

“We’ve been going with a lot of bullpen games and openers, and the lineup that we’re facing here has a lot of lefties,” manager Carlos Mendoza said Saturday at Citizens Bank Park. “It’s a lineup that’s familiar with, he’s had success here before, and we’re going to need these guys. I keep saying it.”

In 13 career games against the Phillies, Peterson has a 5.28 ERA. He’s 0-3 with a 5.40 ERA in eight games (seven starts) in Philadelphia.

The Mets do need their scuffling starters to start turning in quality starts. Peterson, left-hander Sean Manaea and right-hander Kodai Senga are all going through down seasons, though Manaea has pitched much more effectively as of late. With Nolan McLean struggling to find himself after making alterations to his arm slot, and two starters on the injured list, Christian Scott and Clay Holmes, the Mets’ rotation has thrown the fourth-fewest amount of innings in baseball.

Scott, however, may be back soon. The right-hander, who has been down since last week with a hip impingement, joined the team in Philadelphia on Saturday to throw a bullpen. Scott was happy with how it went and said his hip and his arm felt great after throwing with high intensity.

There is a possibility he could avoid a minor league rehab assignment if he’s able to maintain the intensity when throwing to hitters in live bullpens.

“If he responds from this bullpen session, there’s a good chance he’s going to draw an intense live BP with multiple ups that you could say that might count as we rehab [start] because he’ll be facing batters,” Mendoza said. “We’ll go from there.”

Shortstop Francisco Lindor (left calf strain) came through his rehab start with Double-A Binghamton on Friday without incident, as did outfielder Tyrone Taylor (right hip flexor strain). Lindor, Taylor and infielder Ronny Mauricio (fractured thumb) will all play with Triple-A Syracuse on Sunday.

While the end of the injured list might be close for some, for three others, there has been little, if any, progress made. While that’s understandable for Holmes, who had to let the fracture in his fibula heal before starting any baseball activities, the Mets had expected that Jorge Polanco would be back by now, and that Luis Robert Jr. would be rehabbing in the minor leagues.

The situation with Polanco (Achilles bursitis) sounds as though he may be shut down completely at some point, though the Mets continue to say they hope to be able to use him this season. He was pulled off a rehab assignment recently, and it he isn’t close to restarting. Polanco is hitting and he ran the bases Saturday, but over the last 3-4 weeks the Mets haven’t been able to get the first baseman to a point where he isn’t experiencing Achilles pain.

Going through workouts will be fine for the 32-year-old veteran for a few days, but then the Achilles will flare up again, and he’s forced to hit the brakes. He’ll need to take time off, which slows his progress, and the cycle continues.

Robert’s absence has forced some different outfield alignments. The Mets thought they had a solution in A.J. Ewing, and while the rookie has been excellent, he’s struggled to hit left-handed pitching. The 21-year-old left-handed hitter is hitting .302 off righties, but only .152 off lefties. He was out of the lineup Saturday with the Mets facing left-hander Cristopher Sanchez.

Carson Benge played center field and Eric Wagaman started in right field for the first time since last season with the Miami Marlins. The utilityman has made only three career major league starts in right field, but the other two options at the position for the Mets are left-handed, Brett Baty and Jared Young, and the Mets wanted to stack the lineup with right-handers against Sanchez.