Meslier has firmly established himself as Marcelo Bielsa’s number 1 at Elland Road and despite being just 20 years old is now enjoying regular Premier League game time.
He was called into action on a number of occasions at Goodison Park on Saturday evening as Leeds grabbed a 1-0 win over Carlo Ancelotti’s men.
Whelan is pleased with how Meslier is developing as a goalkeeper and stressed he needed to show real concentration at Everton as he was not being constantly tested.
“He was important when he needed to be”, Whelan said post match on BBC Radio Leeds.
“It wasn’t all firing balls at him and he had to be there and being worked and worked, but the chances that Everton had, he had to be fully alert and showing his best.
“That is what you need from him and he’s really maturing into a fantastic goalkeeper.”
Meslier has so far conceded 17 goals in the Premier League, keeping four clean sheets along the way.
He has yet to go beyond a total of 21 senior games for Leeds, but did enough to convince the club to sign him permanently in the summer, while former Real Madrid custodian Kiko Casilla was displaced by the Frenchman.