I also want to mention that he has been discussed quite a lot here, and a search for his name should bring up multiple threads.
The most common mistake I see regarding Beltre is people taking his past stats into consideration without the proper context. Beltre was fighting life threatening illneses over the last few years - that had a much much larger impact than the "contract yr theory"
Seriously though - look at this article written by a reputable fantasy source. Its an article trying to argue both for and against Beltre repeating - but clearly the author is clueless about Beltre's past injury history - he doesnt mention it even once - doesnt even allude to it. The guy lost someothing like 30 pounds as a 23yo because of a botched stomach surgery and the author doesnt even mention it.
Hopefully the link works, but again, its only to show the fact that most people - even so called "experts" dont understand why Beltre "broke out" and still repeat the contract yr theory which may have contributed for a part of it, but not nearly as much as being relatively healthy for the first time in 2 years.