There is no such thing as a pitching prospect.
Mets stud pitching prospect Jenrry Mejia has been diagnosed with a complete tear of the medial collateral ligament in his right elbow, but will seek a second opinion before making a decision about surgery. Assuming the initial prognosis is correct, Mejia can expect the recovery to take a year, give or take a couple of months.
Mejia has been merely decent pitching in Triple-A Buffalo's rotation this year, sporting a deceptively low 2.86 ERA that was hardly supported by his strikeout and walk rates. In 28.1 innings he had walked 14 batters and struck out 21, poor ratios of strikeouts to walks, strikeouts to innings, and walks to innings, and he scarcely made up for it by allowing more fly balls than grounders. Nevertheless, he was the best minor league pitcher the Mets had (though Matt Harvey is quickly making a case for himself) and this is a serious blow to a farm system that was already light on near-ready talent.
Update: Perhaps someone more knowledgeable about this sort of thing can clarify, but the Mets' press release on Mejia's injury calls it an "MCL tear of the right elbow," though the medial collateral ligament is actually found in the knee. A Google search turns up MCL as an occasional synonym for the UCL — ulnar collateral ligament — in the elbow.