PHOENIX — On a day of few positives for the Mets, a displaced starting pitcher finally took a step forward.

Sean Manaea pitched a scoreless eighth inning with two strikeouts in the Mets’ 5-1 loss to the Diamondbacks at Chase Field.

The result was the lefty’s best in several weeks, but the most encouraging sign might have been his velocity.

Manaea, whose fastball has lagged all season, averaged 91.3 mph with his four-seamer.

He was averaging 89.7 mph with that pitch when the day began.

In his relief appearance in Colorado on Wednesday he recorded only one out in the ninth, allowing three hits and plunking a batter.

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That letdown forced manager Carlos Mendoza to use Devin Williams for the final two outs with the bases loaded and the Mets ahead by five runs.

“[Manaea] has been working really hard, you have to give him credit,” Mendoza said. “This is a guy that is not going to put his head down and it’s good to see the fastball, the life and for him to get those three outs hopefully it gets him going.”

Jorge Polanco’s right wrist contusion, for which he was originally placed on the injured list, is “in a good place,” according to Mendoza.

But the first baseman remains on the injured list because of a recurrence of the left Achilles bursitis that limited his mobility earlier in the season.

“There’s some good days and other days when it’s not so good,” Mendoza said.

Luis Robert Jr. is receiving treatment, but has not resumed baseball activity.

Robert has been on the IL since April 27 with lumbar spine disc herniation.

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Kodai Senga threw from a bullpen mound for the first time in his rehab from lumbar spine inflammation.

The right-hander has spent the last two weeks on the injured list.

A.J. Minter, whose rehab was terminated on Wednesday because of left hip discomfort, threw a bullpen session on Saturday, according to Mendoza.

The lefty reliever will throw at least two additional bullpens before he’s considered for minor league rehab games.

Joey Gerber was removed from the injured list and optioned to Triple-A Syracuse.

Eric Wagaman was outrighted to Syracuse after clearing waivers.