Rafael Montero's return to the Majors took a step backward this weekend when he was diagnosed with a strained left oblique, the team said Sunday.
The 23-year-old right-hander suffered the injury pitching for Triple-A Las Vegas on Saturday, leaving his start after throwing just five pitches in an eventual 7-1 win over Oklahoma City.
The No. 2 Mets prospect is 4-2 with a 3.75 ERA in 11 Pacific Coast League starts for the 51s this season. He appeared in four Major League games in the middle of May, but was reassigned to Las Vegas to work on his command after walking 11 batters over 20 frames with the Mets.
There is no word on whether Montero will be placed on the disabled list yet, but Mets skipper Terry Collins was hopeful the injury will not impact the big league club too negatively.
"We're very happy with our depth right now with what we've got," Collins told MLB.com. "We've got certainly [Rafael] Montero, [Noah] Syndergaard and a number of other guys who are waiting for their chance. I like our depth."
Signed by the Mets as a non-drafted free agent in 2011, Montero -- MLB.com's No. 71 prospect -- is now in his fourth year in pro ball. The 2013 season was a banner year for the native of the Dominican Republic, who went 12-7 with a 2.78 ERA between Double-A Binghamton and Las Vegas. He struck out 150 batters over 155 1/3 innings and was named to the World Team at the XM Futures Game at Citi Field.
Montero is the second top pitching prospect to get hurt pitching for the 51s. Syndergaard, ranked 10th overall by MLB.com, injured his non-pitching shoulder covering home plate June 5. Syndergaard will reportedly come off the DL and start for Las Vegas on Monday.