Antonio Conte says Diego Costa is happy at Chelsea and denied that the striker is on his way back to Atletico Madrid.
Costa joined the Blues from Atletico for £32m in July 2014 and enjoyed a productive first season at Stamford Bridge, scoring 20 goals in 37 appearances.
The 27-year-old netted a further 16 times last season but there have been suggestions he may return to his former club, although Atletico president Enrique Cerezo has played down reports talks had begun.
And head coach Conte, whose Chelsea side are on a pre-season tour of Austria, has declared himself a huge fan of the player and wants him to remain in west London.
"For me, Costa is a fantastic player, one of the best strikers in the world," he said.
"We are Chelsea and Chelsea are one of the best clubs in the world and for this reason, I think Diego Costa must stay.
"I see him very happy and I don't know any other situation. Diego Costa is Chelsea's player."
Chelsea were beaten 2-0 by Rapid Vienna at the weekend but Conte has been pleased with the way his squad trained this week ahead of Wednesday's game with RZ Pellets WAC.
"I'm finding players with the right attitude and the right behaviour, who are great workers," he added.
"It is important to have a bit of time to go into a new idea of football.
"There are different aspects - tactical, physical, mentality - so it is important to have a bit of time to meet the players, and for them to meet me and my staff.
"I am very happy this week because I saw a lot of positive things. I saw the right behaviour and attitude of all the players."