The Mets are 13 games under .500 and have less than six weeks to convince their front office they should not sell at the trade deadline.

The season is on life support, to put it generously, but outings from Christian Scott matter even if this year ultimately will not.

In his first start off the injured list, Scott showed some of the same excellent stuff that has made him a bright spot in a dark season.

The 27-year-old threw one regrettable pitch — a 3-2 fastball to Bryce Harper, Scott bemoaning turning to the four-seamer a fifth time in the at-bat — that crept over the wall in left-center in the third inning for a two-run home run and otherwise was in control.

“Really solid,” interim manager Andy Green said after the 6-2 win over the Phillies at Citi Field on Saturday. “Only had so many bullets to fire today, and he was good outside of one swing from Bryce Harper.”

Scott, who had not pitched in a little over two weeks because of a hip contusion, lasted 82 pitches in 4 ¹/₃ innings in which he let up just those two runs on three hits and two walks while striking out six.

The righty, who had missed all of last season because of Tommy John surgery, induced 17 swings-and-misses while leaning particularly on his sweeper and four-seamer.

“I feel great,” said Scott, who owns a 3.20 ERA and looks like a fixture in this rotation for years to come. “Felt like I attacked the zone pretty well for the most part. Just established my offspeed stuff early in the game and then kind of just rode the wave off of that.”

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Zach Thornton’s reward for an excellent start — the kind the Mets are in desperate need of — was an immediate trip back to Triple-A Syracuse.

The Mets optioned the young starting pitcher, who had held the Phillies to one run while striking out seven in six innings Friday, to create roster space for Scott.

Including Scott, the Mets — who have Kodai Senga pitching out of the bullpen and have traded David Peterson — have four starting pitchers.

But they nonetheless demoted Thornton in large part because they have nine innings to cover Sunday without a true starting pitcher (Cionel Pérez will start) in a bullpen game that could feature Kodai Senga.

Rather than removing a reliever from the group ahead of a game in which the bullpen will be taxed — and with an off day Thursday, meaning that a fifth starter (or bullpen game) will not be needed again until July 7 — Thornton received some difficult news the day after his second and best major league start.

“He definitely did well [Friday],” Green said. “It was conveyed to him. Oftentimes these things are just roster decisions that keep your bullpen viable as you go through stretches.”

The 24-year-old Thornton, who began his season at Double-A Binghamton and earned a promotion after just five starts, has been a bright spot in a farm system that has not seen enough breakouts this season.

Top prospects Jonah Tong (5.95 ERA) and Jack Wenninger (6.67 ERA in his past seven starts) have struggled with Syracuse.

Green said he expects “to see Zach back here.”

“He needs to go dominate what’s in front of him and continue to be professional,” Green said, “and I thought it was a tremendous outing from him [Friday].”

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Jorge Polanco went 0-for-3 with a strikeout in the start of another rehab assignment, one that the Mets hope will end differently than the last.

The veteran, who arrived on a two-year, $40 million contract, served as Syracuse’s DH Saturday for the first time since June 5, when his rehab assignment was paused due to ankle soreness.

Polanco originally was placed on the injured list with a wrist contusion April 15 but also has been dealing with Achilles bursitis.

The Mets have said that if Polanco makes it back to the majors, he will be playing through ankle discomfort.

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Infielder Zack Short was outrighted to Syracuse.