The thing is, what we are seeing from those guards is exactly what's expected from their history.
Rondo was expected to be the elite playmaker, and he's been exactly that.
Terry was expected to be a clutch, knock down shooter - he's been exactly that.
Barbosa was expected to be a streaky scorer who will struggle when cold, but can light up the score boards in a REAL hurry when hot - he's been exactly that.
Lee was expected to be a jack of all trades guy who is pretty solid at eveything and not great at anything - he's been exactly that.
Lee is historically only going to give about 10 PPG even in starters minuts if his history is anything to go by. He's not known as a great passer or ball handler, he's known as a solid (if not exceptional) defender. He's also known as a bit of a steaky shooter. All of that is what we have seen.
The only thing that I think will really improve with Lee is his three point shot, which he's clearly struggling with . Even if he starts hitting those shots at his usual rate though, he's still the mmost expenable player on our roster.
Need late game shooting - put Terry in. Need a spark of scoring energy - put Babosa in. Need lockdown defence - put Bradley in.
There is no scenario where you think "this is a perfect time to put Lee in!". Right now the only such scenario is when you need his defense against a strong scoring guard, but that will get redundant when Bradley comes back healthy.