This.
Earn the minutes.
It also helps if your vets aren't openly tanking/pouting. It's a shame that George Hill, Korvor & JR didn't take a professional approach Sexton's rookie year, but it's also a shame that the organization demanded he get minutes right away. Same with Garland, I'd say the same about Okoro, but by that point the ship had sailed and you needed someone, anyone to put in the effort on defense at the 3 you kind of had to go with it.
Even if the bar is somewhat low, having a vet in the way should make guys realize what they need to work on and help shed some of their bad habits.