Petr Cech's superb form for Arsenal this season has been praised by Chelsea interim boss Guus Hiddink.
The Dutch coach worked with Cech during his first spell at Stamford Bridge and believes the 33-year-old remains one of the best goalkeepers in the world.
Chelsea opted to cash in on the Czech international ahead of the 2015-16 season following the emergence of Thibaut Courtois, and Hiddink says Cech's response shows the professionalism of his former player.
"He was and is still [one of the best]," said Hiddink, ahead of Chelsea's trip to Arsenal on Sunday. "These kind of goalies are so determined, so ambitious, so detailed in their work.
"It's difficult to give a judgement [on Chelsea selling Cech] when you're not there at the moment the decision was taken. They had also a strong goalie with Courtois and at certain moments you have to make a decision.
"They made a decision because this upcoming young man had to play as well. It's easy to make a judgement when you are now more than a year [removed] from the decision. But I must say Petr has reacted very well.
"He is doing his job and goalies like this can go on as long as they maintain their fitness, even now at 33. He's a very good example of professionalism. I think he has proven in recent years that he is one of the best in the world.
"In a season even when you are at the top, you are not always good in 38 games. You have a certain period - mostly in October and November when the leaves start falling a bit - that the team might drop, and the good goalies in that period make points for your team. He is doing it."