After a shaky few months, the Italy international is being linked with a return home to Inter Milan. Indeed, an approach from Inter next month for Vicario has been mooted.
But Frank insists he and his staff can help Vicario reach his potential - just as they did for Arsenal No1 David Raya at Brentford.
He said: "He’s a very good goalkeeper, a fantastic shot stopper and he’s saved us a lot this season when we needed him the most. Then like with any goalkeeper, there are a few development areas that we need to do the best we can to improve.
"He had a good level in distribution but it’s a level he could work on and get even better. That’s something we’re working on.
"Every keeper will always be highlighted. David Raya at Brentford in the beginning with some crosses or some distribution that led to goals.
"We worked on it and became better, and then he was sold to a club we can’t name.
"Then Mark Flekken, when he came to Brentford the first six months also took a little bit of time, but he developed which is natural.
"Vic has some of the key areas, Fabian and I identified from the beginning, and he worked very hard and showed some excellent things in terms of shot-stopping."