LOL. I share your facetious pessimism over what seems to be the most unusual injuries to Angel players.
Yes. The patellar tendon rupture is a pretty bad injury. Fortunately, since he is a pro athlete, he'll probably be on the operating table this week. That will help him get back faster. The surgeon will be able to say how he felt the surgery went and any anticipated problems. After that, they should know very accurately what his rehab looks like at the 4 month mark. At about 6 months, I'd expect to see him start at least light pitching. The biggest factor, however, will probably be psychologically. It's not easy to get back to using your leg properly again and fear of re-injury often limits an athlete's return from injury. But assuming the outlook after surgery is positive, I would expect to see him pitching no later than 12 months.
Usually in this situation, there was some sort of patellar deficiency already. Then the pressure exerted on it causes it to tear. This is a pretty bad injury. I can't say that it is worse than an ACL (which is a ligament and must be completely replaced), but it's pretty bad. Very little blood supply there.