Yes, "old-school" coaches tend to think that way, and it doesn't work. That's part of the reason why the Spurs were more successful on defense with Jones in there. His defensive a en is far beyond the other players on the team, which means he can use positioning to cover up his size. Teams starting smaller guards win les all the time. Clearly, it's not actually a liability. It's like how Parker wasn't actually a liability on defense, but coaches kept tricking themselves into going at him without success. Having a bunch of mid-sized players has never been the key to success on defense. Having one of two guys who can cross guard for you? Sure. But it's important to have guys who can guard at all three levels, rim protection and a coaching scheme that gets guys to work together to force the offense into bad shots and secure the board.