Evan Drellich has an excellent article detailing how Chad Qualls fixed his mechanics after a knee injury (that, coincidentally, took place in Houston) and revamped his throwing motion. Luhnow thinks they'll be able to keep those mechanics in place:
We looked at a lot of video and we looked at all the information we have, and we believe he made a few mechanical changes that allowed him to get back to really pitching from his strengths. We should be able to maintain those, so we're comfortable that the success that he had in 2013 is going to be continued.
Click the link.