Willy Caballero has praised Kepa Arrizabalaga for how well he has adapted to the Premier League and believes it is "crazy" to talk about his £72 million (€80m/$92m) transfer fee, given how the market has changed in recent years.
The Blues raised a few eyebrows in the summer as they paid a world-record sum for a goalkeeper, with Kepa coming in to replace Thibaut Courtois following his switch to Real Madrid.
However, the Spaniard has shown no signs of needing time to adjust to the Premier League having avoided any high-profile errors thus far and has quickly established himself as a reliable No.1 for the club.
Even in spite of his team's inconsistency he has been able to move into second place in the race for the Golden Glove, ahead of Manchester City goalkeeper Ederson.
Still just 24, Caballero is 13 years his senior and he insists he has been impressed with what he has seen from his team-mate.
"First of all, we needed a goalkeeper who plays really well with his feet," Caballero told Goal. "He is doing really well with that; he has confidence and a good pass. Long and short.
"As well as that, he has very quick reactions, good hands and he is doing well. I thought he might need a few weeks and months because adaptation to the Premier League sometimes needs a little bit of time but from the first game, he has been doing really well.
"I think that football has gone crazy in the last three or four years. When we talk about a player for the money that we spent, in this market, I think it is a little bit crazy. We shouldn't talk about money, we have to talk about his performances and I think his performances have been really good."
The goalkeeper was known to have played in midfield at Athletic Club, thus honing his ball skills ahead of joining Maurizio Sarri's side in the summer.
And the Chelsea boss told reporters last week at Cobham training centre that he believes he is managing a goalkeeper who is destined to reach the top of the game.
"It's different [in England]. So, it's not easy for a young Spanish goalkeeper to adapt himself to this championship," he said ahead of the defeat to Bournemouth. "But he improved very fast. He will be one of the best goalkeepers in Europe in the future.”