NEW YORK -- The Orioles will be without one of their more promising pitching prospects for a while.

The club announced Tuesday that right-hander Zach Pop, its No. 19 prospect per MLB Pipeline, has undergone Tommy John surgery to repair the ulnar collateral ligament in his right elbow. Dr. James Andrews performed the operation, and Pop is expected to be sidelined for all of 2019 and part of the '20 season while he recovers.

The injury comes after a concerning first spring with the O's for Pop, who was part of last summer’s package deal for Manny Machado. The 22-year-old right-hander had allowed a run over his first eight games at Double-A Bowie this season, but he hadn't appeared for the Baysox since April 30. Pop was also briefly shut down in March after his fastball velocity dipped into the upper 80s, an issue he and the club said was due to fatigue.

It's unclear if the incidents are related. Durability has been a concern with Pop for some time, after a right forearm strain wiped out the second half of his junior year at the University of Kentucky in 2017. The Dodgers made him their seventh-round selection that June anyway, betting that his high-velocity sinker and plus slider might help him grow into an impact late-innings arm.

Pop has been just that over parts of three Minor League seasons, both before and after the Orioles acquired him in a six-player deal for Machado last July. His three-quarter arm slot makes him particularly lethal against right-handed hitters, whom he held to a paltry .162/.243/.200 line in 2018. It also helps make Pop something of a ground-ball machine; His 65.8 percent ground-ball rate ranked sixth among all Minor League hurlers in 2018, and he surrendered just one home run across his first 80 1/3 professional innings.