Mitre is their only MLB option.
As for the AAA options
In the AAA ranks, Hirsch is pitching like a man on fire. Remember, he once was a big prospect who flamed out in the elevation in Colorado Springs and Colorado. He still throws well with good stuff, so he is probably first in line. He has a WHIP under 1 and an ERA right around 3.
The next option would be Ivan Nova, but they would probably want to hold off until later in the yr. Nova is a guy with great stuff who is finally starting to pitch to his ability. Setting him back with a poor MLB showing could be career killing.
The final option, and probably the best long term option is Zach McAllister. He's a sinkerballer with impeccable control, the only problem is that he has been hit quite hard in his first taste of AAA
So, if Vazquez is out for an extended period of time, Mitre would step in. If Pettitte needs to hit the DL, my bet is that Hirsh takes the hill