Former Mets prospect Brandon Sproat gives up grand slam four batters into nightmare Brewers debut

Every pitcher’s worst nightmare came true for Brandon Sproat.

The former Mets prospect stepped up to the mound for the Milwaukee Brewers’ series finale on Sunday against the Chicago White Sox, allowing back-to-back walks and a single, leading to a grand slam by Colson Montgomery four batters into the first inning.

Sproat, 25, did recover to get out of the inning, but ultimately ended the game in unspectacular fashion.

The former high-profile prospect completed three innings with seven earned runs and six hits allowed, along with four walks and three home runs.

The effort gives him a dubious 21.00 ERA on the very young season thus far.

Sproat, of course, was the crowning part of the Brewers’ return in the Freddy Peralta trade this offseason.

The full deal saw Sproat and Peralta exchange homes, with fellow pitcher Tobias Myers also coming to wear orange and blue, while Jett Williams — another top prospect while with the Mets — was sent to the Midwest.

Williams is starting his season in Triple-A.

Peralta started in the Mets’ season opener on Thursday, resulting in an 11-7 victory for the Amazin’s.

The Moca, Dominican Republic native got off to a shaky start but recovered to record his first win as a Met, completing five innings and allowing four earned runs, striking out seven hitters along the way.

Myers also pitched three innings in the season opener, allowing just one earned run — a home run — and one strikeout in his Mets debut.

Notably, Sproat allowed a home run to Japanese signee Munetaka Murakami, who now has three homers in his first three Major League Baseball contests.

Murakami, 26, signed a two-year, $34 million deal this offseason with Chicago.