As one of the top hitting prospects in the Mets farm system, Mark Vientos doesn’t have much experience pinch hitting. 

Now that he’s on the major league roster in Queens, playing time is harder to come by — at least for now — so Vientos has had to figure out ways to be valuable. 

He succeeded in Thursday’s 4-2 win over the Phillies as he drove in a run by hammering a sacrifice fly to center in the bottom of the sixth inning to give the Mets some breathing room as they completed a sweep of their NL East rivals. 

“It’s an adjustment, honestly,” Vientos said of his new role coming off the bench. “This game is all about adjustments… and I feel like I’m doing a good job.” 

The 23-year-old had been 0-for-2 in pinch-hit appearances with the Mets this season, but Buck Showalter has said he wouldn’t be afraid to go to the righty-swinging Vientos in the right spot, regardless of how early it is in a game. 

On Thursday, it came in the sixth. 

Vientos, though, started getting ready an inning earlier when the left-handed Matt Strahm replaced starter Taijuan Walker, a righty. 

The sixth developed perfectly for Vientos as Brett Baty led off with a double and Starling Marte followed with a sacrifice bunt to send Baty to third. 

Showalter went to Vientos to hit for Daniel Vogelbach and Vientos got Strahm to a full count before sending a shot to deep center. 

“Before that at-bat happened, I was thinking about a situation with a runner on third and I come up and did exactly what I wanted to do,” Vientos said. “Make hard contact or hit a [fly ball] or a ground ball through the middle, just to score the run. That was my job and that’s what I wanted to do.” 

He also took care of the hard contact part of it as he drilled the sac fly to deep center, measured at 112 mph off the bat, Vientos’ highest exit velocity as a major leaguer. 

“I felt like I hit it hard,’’ Vientos said. “I was talking to the ball to go over [Brandon Marsh’s] head [in center], but it got the job done.” 

The Mets are scheduled to face two righties to start their next series against Toronto and the Mets haven’t given up on Vogelbach yet, even though he doesn’t have an RBI since May 9. 

Vientos, Baty and Francisco Alvarez have proven to be key contributors to the offense, and perhaps Ronny Mauricio will be, as well, at some point this season. 

But as long as Vientos isn’t in the lineup every day — and he’s started seven of the 10 games he’s appeared in since being called up from Triple-A Syracuse — he’ll have to have value in his current role. 

“I just take it as I’m playing every day,’’ Vientos said. “I’m watching every pitch, asking questions [of] teammates about the game. I try to stay as locked in as much as possible. 

And Thursday, the results were good. 

“It’s hard work paying off,’’ Vientos said.