Nkunku, signed from RB Leipzig in a £52million deal in the summer, spent six months on the sidelines after suffering a knee injury which required surgery in pre-season.
He made his long-awaited debut off the bench against Wolves on Christmas Eve, featuring in Chelsea’s next three games but was absent from the squad for Saturday’s FA Cup third round clash with Preston.
Pochettino revealed post-match the France international missed out due to a hip problem which is set to rule him out of Tuesday’s Carabao Cup semi-final first leg clash with Middlesbrough.
Nkunku has not returned to training since the hip problem emerged last week and while the club will continue to exercise caution over his return, Pochettino is confident it is not ‘a big issue’.
Speaking at a press conference on Monday, the Chelsea boss said: ‘No set back, it is not related to his previous injury.
‘It is a different problem, an issue in his hip, not his knee. Now we have to be cautious with him because it was six months that he was not involved.
‘He is not going to be involved tomorrow, we will see for Saturday but we are not sure, we are going to be cautious with him.
‘Hopefully it is not a long period. But at the moment he is not training, he is doing recovery. But it is not a big issue.’
While the trip to Middlesbrough will come too soon, Chelsea will hope to have Nkunku available for the visit of Fulham next weekend.
Nicolas Jackson meanwhile has departed for the Africa Cup of Nations with Senegal.
The Lions of Teranga begin their campaign against Gambia on 15 January.
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