Robert’s extra-base hit — which scored Alonso from second base — gave Baltimore an early 3-0 lead at Coors Field.

Robert went 1-for-5 with two RBIs in his Baltimore debut, including scoring the go-ahead run as a ghost runner in the top of the 11th inning on a Samuel Basallo RBI single.

However, the Orioles fell to the Rockies in the bottom half of the frame on a bloop two-run single to left field that fell in front of Robert, with him failing to throw out the winning run at home, in a crushing 6-5 loss.

The loss put the Orioles two games back of the third American League Wild Card spot.

The waiver claim of the 29-year-old Robert allowed the Mets to shed $5 million — between the money left on his contract and a buyout — and gave the surging Orioles a potent bat for the final month of the regular season.

Acquired from the White Sox in the offseason, Robert got off to a strong start with the Mets before a back injury sidelined him for three months.

Even with a torrid stretch in August, Robert managed just a .223/.303/.399 slash line with 10 home runs and 23 RBIs in 58 games.

“I think he closed out the chapter really well,” interim manager Andy Green said Monday at Tropicana Field.

“Certainly, the chapters that preceded the last one were frustrating from an availability perspective.”