Nkunku joined Chelsea in a PS52m deal from RB Leipzig in 2023 but he only made 11 Premier League appearances last season due to injury issues.
The 26-year-old impressed in pre-season under Enzo Maresca and looked set to play a key role in the Italian's new-look side but has not started a Premier League game since the opening day of the season.
Only afforded starts in cup competitions, the Frenchman has still proved his worth, notching up nine goals in seven games in the Carabao Cup and Conference League combined.
However, reports suggest that the forward is growing increasingly frustrated at his lack of league minutes, with Manchester United one of the clubs credited with an interest if the Blues look to move Nkunku on.
But former Tottenham midfielder O'Hara believes the club should not even think about selling Nkunku and said the forward must learn to wait his turn.
'Chelsea should absolutely not be selling Christopher Nkunku,' O'Hara told Grosvenor Sport. 'He's a top player and they can't be getting rid of him in January.
'Nkunku just has to deal with it - he was injured all of last season and has come back this year, so he needs to fight his way back into the team.
'Chelsea are doing well and are in a good place at the moment, so Nkunku just needs to accept it and fight for his position.
Earlier this month, former Blues defender Glen Johnson echoed O'Hara's sentiment, insisting that Nkunku would be 'mad' to consider leaving Stamford Bridge at this point of his career.
'His start to life at the club was quite tough when he suffered his injury and we don't know if he's fully over that yet,' Johnson told Betfred.
'They're in a much better position now and if he can get fit and get himself in the starting eleven, then Chelsea have a good player on their hands. He just doesn't look fully fit yet.'
Nkunku featured in both matches for France over the most recent international break - starting in a 3-1 away win against Italy - but was unable to get on the scoresheet.
The forward will hope to force his way back into Maresca's first-team plans when the Blues travel to face Leicester City in the league on Saturday.
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