Rangers GM Jon Daniels says Matt Harrison has a herniated disk. Will have back surgery Tuesday.— Anthony Andro (@aandro) April 19, 2013
The back surgery will likely be a microdiscectomy, given the relatively short return time. The surgery will be performed in Dallas by Dr. Drew Dossett, one of the country's top back surgeons and a protege of Dr. Robert Watkins.
A microdiscectomy is a surgery in which the spinal surgeon or neurologist goes into the spine through a tiny incision and removes a small part of the damaged spinal disc using special tools. These spinal discs act as cushions between the vertebrae, so removing only the damaged or impinging part leaves much of the cushioning effect in place and results in less trauma.
In the case of Harrison, Anthony Andro also gave the location the doctors will repair:
L5-S1 is the disk that's bothering Harrison for those of you who know what that means. To me, it's lower back.— Anthony Andro (@aandro) April 19, 2013
This area is very low on the spine, as shown in the picture to the right. It is a common region for this type of herniation to occur. Given the stress on the lower back due to pitching motion, it is not an uncommon injury among pitchers.
It also very clearly explains why Harrison lost some velocity, as this damaged disc would have prevented a full bend and changed his release and follow-through.
Harrison will miss around two months, putting his return to the Rangers' rotation around the All-Star break.
Pitchers that miss this much time and are unable to continue throwing will need an extended rehab period. The Rangers do most of their rehabilitation at nearby Double-A Frisco, allowing the major league staff to monitor the players.
Frisco athletic trainer Carlos Olivas also has an excellent reputation and a track record of positive results with major league rehabs.
In the meantime, the Rangers will continue to use young pitchers Nick Tepesch and Justin Grimm.
Two injury cases that could be back in the near future are Colby Lewis, coming off elbow surgery and expected to start a rehab assignment at the start of May, and Martin Perez, who looked to break camp with the Rangers until a come-backer fractured his wrist.
Perez is in the midst of a throwing program and could begin rehab starts—again, likely in Frisco—within the next 10 days.
Harrison should have no trouble returning once he completes the rehabilitation program following surgery and regains the stamina in his arm. Pitchers such as Randy Johnson, Kevin Brown and Eric Gagne and players like Rafael Furcal have had similar procedures and returned on schedule.