Mark Vientos dug himself a hole.

He was down, 0-2, in an at-bat that looked like a lot of his at-bats early in his major league career.

But what followed veered from the script.

The Mets rookie fought back.

As Vientos is learning through a lost Mets season, maybe he can become a find.

The rookie put together quality at-bat after quality at-bat that helped bring the Mets over the sloppy Reds, 8-4, in front of 38,044 at Citi Field on Sunday afternoon.

Vientos smacked three balls hard, but it was the approach more than the outcome that impressed most.

With two runners on base in the fifth inning of a game the Mets were leading by one, Vientos stepped up against Carson Spiers, a righty (notable for the righty-hitting Vientos).

A couple of sinkers provided the first two strikes of what would have been his 58th strikeout in his 186th plate appearance, more than one-third of the time.

Instead, Vientos laid off an inside fastball.

He watched Spiers miss with a slider inside and then a sinker outside.

With the count full, Vientos shortened up and smacked a cutter right back through the middle for an RBI single, giving the Mets a valuable insurance run and giving the Mets more reason to give him more at-bats.

Vientos clearly has mastered Triple-A pitching, posting a .999 OPS with 16 home runs in 61 games with Syracuse this year.

He is beginning to show his bat could be adapting to big-league pitching too.

After his 3-for-4 afternoon, Vientos is hitting an even .300 (15-for-50) with three home runs and six RBIs in his past 14 games.

None of his hits Sunday were soft, turning exit velocities of 104.1 mph, 105.2 mph and 100.4 mph into three singles.

Vientos entered play with an average exit velocity of 93.3 mph, which was 11th best among hitters with at least 100 plate appearances. It’s only going up.

Vientos’ iffy glove makes his bat paramount to earning playing time. Among his competitors at third base, Brett Baty could return from a hamstring injury Monday and Ronny Mauricio added a pair of singles Sunday.

His competition at DH impressed too.

Daniel Vogelbach, who has quietly had a huge second half after a small first half, pinch-hit in the seventh inning and cleared bases that had been loaded with a double off the center-field wall to blow the game open.

A couple of the Mets’ potential designated hitters for next season — as well as three errors from the Reds’ defense — helped make a winner of Jose Quintana, who allowed two runs in 6 ⅔  strong innings and holds a 3.02 ERA after 11 starts.