Rogic netted a last - minute winner in Celtics ' 4 - 3 win at Motherwell .
The Hoops mentor says the 23 - year - old is only going to get better .
Rogic netted a last - minute winner in Celtics ' 4 - 3 win at Motherwell and the Hoops mentor says the 23 - year - old is only going to get better .