As Costa completes his move to Atletico Madrid, Cahill feels the manner of his departure should not overshadow his contribution to the club.
“All the Chelsea players wish Diego the very best," he said. “I'm sure he will go on to do fantastic things at Atletico. He is going to settle in there again. I can speak personally about my experiences with Diego and we won trophies together - it's as simple as that.
“Everyone in their career moves on eventually. Whatever happened has happened, but for the period of time he was here, he was fantastic.
“We were successful together and I will take that, those great memories. People leave, but we don't forget them and we don't forget what they have done."