Long is likely to have his choice of clubs during the close season if they can match Reading's £4million valuation.
Tardelli said: "I think he will be the key man in the transfer window. I see him as a Premier League player now and I think one team will come and buy him.
"He's very good now. Shane physically has become very strong, he's not scared, he's very fast, he reads the game better and he has changed. He has improved.
"He is like Aiden McGeady. When we arrived here they were very shy but now they are very strong. The experience in Russia has been very good for McGeady.
"Shane will be very sad. We saw the match and he played well but football is fantastic because after two or three days everything can change. We know Shane Long will be sad but he will be fine."