PITTSBURGH — Blade Tidwell’s three appearances in the major leagues may not have been particularly clean or particularly dominant, but when he takes the hill against the Brewers during the Mets’ upcoming homestand, the rookie will have at least one extra advantage: a shred of advanced notice.

By virtue of the Mets’ injury-riddled pitching staff, Tidwell, who pitched 3 1⁄3 innings of relief in the Mets’ 9-1 loss to the Pirates on Friday, hasn’t necessarily been shown the blueprint for success. He had a heads-up for his major-league debut against the Cardinals in May but had a surprise call-up the day before a spot start against the Phillies and again was thrust into action Friday after David Peterson’s abbreviated start.

“I’ve had time to work with the coaches here and they’ve been great,” Tidwell said of the difference. “I like to look at the other team and it also just helps being in one place. It helps a lot with how your body feels and being prepared.”

Despite the clunky relief outing — he allowed four runs and five hits with two walks and one strikeout Friday but was mostly victimized by a mistake pitch that Bryan Reynolds blasted for a three-run homer — Carlos Mendoza confirmed that Tidwell, the franchise’s No. 14 prospect, still is penciled in to take Griffin Canning’s spot in the rotation.

Tidwell is 0-1 with a 10.13 ERA in 10 2⁄3 innings but has shown flashes of his potential, particularly against that potent Phillies lineup. Though he clearly still needs development, the Mets’ current pitching picture is conscripting plenty into duty, ready or not. He has a 4.76 ERA in 13 games with Triple-A Syracuse this season.

If all goes according to plan, this week will be his first appearance at Citi Field; his family is planning to make the trip from Tennessee.

“He got hit, obviously,” Mendoza said of Tidwell’s performance Friday. “Obviously, [it’s an issue of] execution. He left a slider up to Reynolds for the three-run homer, but overall, stuff-wise, the velo was there . . . I think he’ll learn from it.”

For what it’s worth, it sounds as if he already has.

“I learned that when you make mistakes, it’s more likely to get hit,” he said. “There’s always a good bit of jitters, but that’s a good thing, because you can either use it to help you or use it and have it hurt you. Really, it’s about getting comfortable in the league and executing pitches.”

Sean Manaea (elbow) is scheduled to throw a bullpen session Sunday after playing catch Friday, though the plan after that remains murky. The lefty, who went down with an oblique injury in spring training, was nearing a return before an MRI discovered loose bodies in his left elbow last week. President of baseball operations David Stearns called it a minor setback and said Manaea likely will need one more rehab start this week before returning to the active roster, but that remains up in the air. “Especially with what he’s dealing with now — bullpen tomorrow and we’ve got to wait to see how he responds,” Mendoza said. “Then we’ll make that next decision.”

Brooks Raley (Tommy John surgery) had his rehab assignment moved to Double-A Binghamton and pitched Saturday. In 1 2⁄3 scoreless innings, he allowed a hit, struck out two and threw 17 pitches (12 strikes). Mendoza said it’s likely he won’t return until after the All-Star break. Earlier this month, Stearns said the reliever probably would take close to the full 30 days on his rehab clock because of his lengthy absence, which would take him to the first game after the break, July 18 . . . Jesse Winker (oblique) will commence his rehab assignment with High Class A Brooklyn on Sunday.