After saying what I said last night about just getting the surgery, I was intrigued by this subject so I did some research on PRP. It turns out that the success rate of this procedure is higher than I thought. This is an excerpt from a paper penned by, among others, the late Dr. Yokum. They ran a study on 34 people who had partially torn UCL's(16 of them pitchers). All of them went through approximately 2 months of treatments outside of surgery to try to get back on the field. The doctors ran them through a battery of tests to get a baseline reading on their injury then ran them through PRP treatments.
On average, it took the players an average of 12 weeks to get back on the field and only one of the 34 ended up needing TJ. They followed up on all of the 34 players over a span of 70 weeks and 30 of the 34 returned to the same level of production they had before their injury.
The link to the paper is here if anyone wants to read it.
http://ajs.sagepub.com/content/early/2013/05/10/0363546513487979.abstract
Baseball Prospectus summarizes it here.
http://www.baseballprospectus.com/article.php?articleid=21067
So, this is what Tanaka faces. If the average is 12 weeks that puts him in the start of October to get back on the field. Based on this information, it would be best if they just shut him down for the rest of the season.