I don’t think “they only played 30 minutes” is the correct answer.
First, any rest is good rest. Playing 25 minutes is better than 30, etc.
But, moreso, it just seems unnecessary at some point. There’s no real reward having the starters in in some of these blowouts. There’s no reward, but there is a risk: injury.
Perhaps I’m paranoid, but I’d much rather have Tatum on the bench goofing off with his teammates than I would have him suffer a useless injury in meaningless minutes.
