I'm pretty sure Ray had an injury in the Orlando series and I think it was his hamstring. If I remember correctly I think he was also wearing a wrap around his leg. Besides that series he had a very efficient year.
Yeah, Ray (or Doc? or both?) acknowledged that he played injured in the Orlando series. Sure, he played badly in this series and suffered from the cumulated fatigue against good defenders (Courtney Lee, and Reddick, who was surprisingly good on D). But Ray also hit a huge shot when asked to, in game 5.
Overall, he had a great season (as shown above with his stats) and good playoffs. Ray basically saved us in the Bulls series, and his 51 points performance was huge, it's amazing to see how sharp he was that night when you re-watch the game, he looked like he couldn't miss the basket.
Hopefully he will get more rest next year, thus being more effective and avoiding slumps (though the slumps are unavoidable, they just last longer sometimes).