I think the stamina issue is related to the fact he ships punishment. If he keeps it at range and doesn't keep getting clipped I fancy him to do alright.
Another big factor is how big Chavez is. If he comes in as a cruiserweight again it could be hard work for Lee no matter how well he boxes. In the back of my mind though I do feel that Chavez Jr is going to come unstuck with his weight draining sooner or later. The fact they flew Ariza out because he had ballooned so badly, then fired him could be an alarm bell, especially with his history of using illegal diuretics. I can see him ending up as an absolute shell like ODLH in the Pac fight.