Jose Mourinho sees no reason why Diego Costa's future is subject to speculation, but declined to say if the striker will start in Saturday's Barclays Premier League game against Bournemouth.
Costa dropped to the substitutes' bench for last week's draw at Tottenham and threw his bib in Mourinho's direction when it became apparent he would not feature at White Hart Lane.
Speculation has heightened that Chelsea are looking to recruit a new striker in January and that Costa, who has three Premier League goals this season, was nearing the end of his time at Stamford Bridge, 18 months after his ?32million move from Atletico Madrid.
Mourinho said: "I don't know why. For me no question marks. Always played, was on the bench one match, which I think is more than natural. No problems, no problems at all.
"I think he always tried to give his best, sometimes playing phenomenal, other times not so well. But he is a player that always tried.
"I didn't ask him (his reaction to last Sunday), but he trained very well. That's the only thing that matters to me.
"I cannot say better than ever, because normally he trains very well."
Costa was one of three players, along with Ramires and Kenedy, pictured on a night out in the early hours of Thursday morning.
The trio were out as part of the squad's Christmas party which had the full blessing of Mourinho.
"The paparazzi was not the best," Mourinho said.
"I think the paparazzi had a problem with the memory card. There were 25 players inside and he only got three."
Mourinho hopes the dinner, followed by a trip to a nightclub, has benefits for the dynamic of a squad, boosted by the availability of goalkeeper Thibaut Courtois after a three-month absence with a knee injury.
"I think they need that and many times so many circumstances it's not easy to do it," he added.
"They told me the dinner was really good and the after dinner was even better. Everybody was happy."
Asked if the management team would have a night out, Mourinho added: "I'm tired of them."
Like Costa, Mourinho has been linked with a move away from Stamford Bridge, this time with a switch to Valencia at the end of Gary Neville's short-term deal.
"The (Valencia) owner (Peter Lim) knows me very well," said Mourinho, who wished Neville well in his role.
"He knows I don't want to move and I want to stay at Chelsea. There is no point. I don't speak about Valencia."
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