I really don't get his move back up to 170. He lost 1 fight at 155 and that was to BJ Penn and he really had no chance in that fight from the get go because he got taken out on the feet. It had nothing to do with his strength and everything to do with his wild, sloppy stand up. His battle with Guida may have got him FotN award, but it also illustrated his sloppy boxing.
He had 3 fights at 155. Stevenson, Guida and BJ Penn. In which of those fights did we see lack of strength as a factor anywhere?
At 170 we've already seen his lack of strength in the Hathaway fight. I can tell you where we are gonna see lack of strength and that is if he ever fights Kos again, or Alves, or Story or GSP.
I saw the UFN weigh-in pics and it looks like the same 170lb Diego to me. He looks like a flabby, undersized WW and several inches shorter than Kampmann.
I'm not saying that Diego can't have success at WW with certain match-ups that favor him, but there's no way he's going to be a contender at his size, where he definitely was at 155.