Mark Vientos a late scratch for Mets as he fights to hold onto job

Carlos Mendoza planned to let Mark Vientos play through his struggles — penciling him in at third base, and hitting second, for Friday’s series opener against the Dodgers — but the 25-year-old was scratched from the lineup for “precautionary reasons” roughly an hour before the scheduled first pitch due to abdominal soreness.

Vientos, who served as DH in this week’s three-game set in Boston, was replaced by Brett Baty, making his fourth straight start at third base.

Baty has been brilliant in the field this season, making one error in 89 chances between third base and second base, while Vientos’ six errors rank among the highest in the majors at his position.

“I wouldn’t say [he’s] pressing, I just see it as, the same way they go through struggles at the plate, they go through it defensively, sometimes,” Mendoza said.

Mark Vientos was a late scratch from the Mets lineup. Jason Szenes/NY Post

“A couple of missed plays here and there, especially some routine plays, maybe he’s thinking about that, but I don’t think he’s pressing because of the situation with Baty. Not at all. These two guys came up together. There’s always been a healthy competition. They root for each other. I don’t see it that way. If he continues to work hard, he continues to put in the effort, he’ll be fine.”

Vientos has also struggled to find the stroke that produced 27 home runs and an .837 OPS in 111 games last season.

Entering Friday, Vientos was hitting .232 with five home runs and a .674 OPS in 168 at-bats, having gone deep only once in May.

Through nearly two months, the Mets rotation has posted the majors’ best ERA.

Soon, the ceiling will grow.

Veteran Frankie Montas is scheduled to begin a rehab assignment on Saturday with High-A Brooklyn.

Mendoza said Montas — who suffered a lat strain in February after signing a two-year, $34 million deal with the Mets in the offseason — is expected to pitch two innings (30-35 pitches) after throwing live batting practice last week.

Brett Baty is getting more time at third base. Jason Szenes / New York Post

Mendoza also announced that Paul Blackburn (knee) will make one more rehab start for Triple-A Syracuse on Tuesday. Blackburn, 31, has posted a 3.91 ERA in six minor league appearances this season.

Scratched for precautionary reasons with abdominal soreness

The Mets released reliever Sean Reid-Foley.

Reid-Foley showed potential last year before a shoulder injury cut his season short, posting a 1.66 ERA in 21 2/3 innings with the Mets.

This season, the 29-year-old struggled in 15 games with Triple-A Syracuse, recording an 8.36 ERA.