The Czech Republic U21 international spent last season on-loan with Blau-Weiss Linz in Austria.
Lee said of the 21 year-old shot-stopper: "Radek has done great out there in Austria.
"He got an injury early on but recovered extremely well and played really well. He has got really good experience there.
"I think we often use Radek as an example to some of the younger goalkeepers in the Academy. He is a player who maximises every part of the programme to ensure he is the best he can possibly be."
Vitek's deal with United runs to 2027.
Consumate professional
Lee also told manutd.com: "Nutrition, gym, analysis. He is the consummate professional and that is going to take him, I believe, to the top level.
"He is a talented boy and that needs to be said. He's 6ft 6ins and that always helps! For the other lads, their challenge is to be as good as Radek and do everything he does and more.
"He is a great example of someone who does that."