Chelsea forward Diego Costa has admitted he remains grateful to former manager Jose Mourinho for helping him become the best he could be during his time at Stamford Bridge.
Speaking to Sky Sports ahead of Chelsea's visit to Manchester United on Sunday, Costa revealed that Mourinho's former presence at Stamford Bridge was a big factor in him deciding to join the club in the first place, while he claimed Mourinho high standards ensured Costa was able to excel after joining from Atletico Madrid.
He said: "In all honesty I always tell people that I am grateful to Mourinho because he helped me a lot.
"As a player when you want to improve you always look for the best coach and Mourinho is one of the best. I wanted to come to Chelsea because of Mourinho. When I considered Chelsea I thought about the fact that Mourinho was here.
"He is a coach that demands a lot from his players, he wants the maximum. He helped me a lot and then what happened is that the following season didn't go well, these things that happen, but the truth is that Mourinho helped me a lot to improve as a player."
Mourinho was sacked by Chelsea after winning the Premier League title in 2014, with the club's form and league position drastically falling in the following campaign. Costa is preparing to face up to his former boss at Old Trafford on Sunday, with Mourinho's Manchester United looking for their first victory of the season over the current league leaders.