Chelsea forward Christopher Nkunku missed Saturday's 4-0 win over Preston North End in the FA Cup due to a hip problem, Blues manager Mauricio Pochettino revealed.
Nkunku has made just four appearances and only start since signing from RB Leipzig in the summer due to a knee injury and there are now question marks over his fitness again ahead of key dates for the west London club.
The Blues are away to Middlesbrough on Tuesday in the first leg of their Carabao Cup semi-final, with the return to take place at Stamford Bridge two weeks later.
In between those cup clashes, Chelsea are at home to Fulham in the Premier League next Saturday, with a visit to Anfield to face Liverpool ahead on January 31st.
"He wasn't involved because he suffered after training a problem in his hip," Pochettino said after Saturday's game.
And not sounding overly optimistic about the 26-year-old's fitness, he added: "We need to see if he can be ready for the next few games."
After a goalless first half on Saturday, Chelsea stormed to a comprehensive victory in the end over Championship side Preston.
Armando Broja, Thiago Silva, Raheem Sterling and Enzo Fernandez scored the goals which sealed a place in round four for the Blues.
Pochettino's side will discover their rivals in the next round in Monday night's draw.
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