Jose Mourinho has confirmed that Diego Costa will start for Chelsea against Aston Villa this weekend, although he is far less certain if the striker will be available for the Champions League encounter with Sporting that follows.
Costa has been in supreme form for Chelsea since his £32 million summer transfer from Atletico Madrid, scoring seven times his first four Premier League games, but the Spain international has been hampered by a niggling hamstring problem.
It is a long-standing issue for Costa, and one that resulted in his withdrawal from the Champions League final this season, although it has yet to have any considerable effect on his performances for Chelsea.
Costa was forced out of international duty with Spain during the recent break, but was fit and firing upon his return to Stamford Bridge. But Mourinho has been sure to manage the player, choosing not to start him for the draw with Schalke.
The Chelsea manager will find himself with a similar selection dilemma when Chelsea travel to Lisbon for their encounter with the Portuguese giants, and he claims to be unsure if Costa will be fit enough to feature.
"He plays tomorrow [against Aston Villa] and he starts the game without problems," Mourinho said at his pre-match press conference on Friday.
"The question is always the same: can he finish the game and be in condition to play in Lisbon 48 hours later?
"It is a question that, in this moment, I don't know [the answer] because I don't think about Sporting and the Champions League, I think about Aston Villa and the Premier League.
"Everybody is working hard and he is the first one to do that. He works with the technical staff and the medical department, he works with the physios.
“He's trying to be ready for every game because mentally he is ready for every game. Physically he's not so everybody is trying hard for him to be able to play every game."
If his early form is any indication then Costa’s fitness will be a key factor in determining the success that Chelsea can enjoy this season, and they way in which Mourinho is able to manage his workload will be particularly important.
Mourinho would have felt as though he already had enough firepower in his squad to overcome Schalke, a game Chelsea should have won, and he will feel the same regarding Sporting.
But, should Chelsea progress in the competition as expected, then Mourinho’s decisions become much more difficult. Were Chelsea to reach the quarter-final stage, then the will play Manchester United, Arsenal and the second leg of the last eight in the space of seven days.
With Premier League and European ambitions to manage at this late stage of the season, Mourinho could be given a significant headache deciding when best to use his premier marksman.