The Eintracht Frankfurt wing-back is in advanced talks to sign Juve this week.
Bojinov told Sky Italia: "Kostic can play in many forms, in a 3-5-2 he would be able to do the whole range. If Juventus catches him he will make a big blow, seeing his last years he has been able to make a big difference in Frankfurt, but also in the Serbian national team.
"When you arrive in a great team like Juve, you are one of many: you leave, then those who do well play.
"In the case of (Dusan) Vlahovic, I say that he is a golden boy and that I admire him a lot. I hope he plays well and shows his value, but Juventus need to have someone by their side. They cannot play 45-50 games alone."