Nate landed jabs, but he was still pushed back and ate the harder shots. And this against a head hunting, sloppy McGregor.
Also, what is this nonsense about Diaz holding back? This isn't anime, man. You don't 'hold back' when you're getting your face bashed in. That wouldn't make any sense, as Nate is an experienced fighter who should know the risks of 'holding back'. Also, it's incredibly patronizing to both fighters.
McGregor was clearly gassed by the end of the first. It's obvious when you take a look at how much he slowed that second round.
If we're going to make ridiculous predictions then I'm going with second round tko by hooks to the body, oblique kicks and roundhouse gut kicks.