The young player partially tore his UCL, which will keep him out for the rest of this season. However, it doesn't seem like he'll undergo Tommy John surgery because he tweeted:
Thank you everyone for the kind words and support. I may be done this year, but I will be back next year for April 1.— Matt Harvey (@MattHarvey33) August 27, 2013
However, GM Sandy Alderson didn't know anything about the tweet, but said that must be the case if it's what Harvey tweeted.
Maybe we'll get some awesome videos and pranks from him in the meantime.