Gabriel Magalhaes would have to pick a new shirt number when he completes his Arsenal move, the UK Mirror reports.
The Brazilian defender has agreed to a five-year deal with the Gunners, after reportedly passing his medicals.
Magalhaes is expected to line up alongside William Saliba in Mikel Arteta’s first full season in charge.
Both Saliba and Magalhaes were among the top young defenders in Ligue 1 last season. But Saliba benefitted from getting to Arsenal first and took the No.4 shirt.
This means Magalhaes will not be able to wear the number which has brought him so much success at Lille.
Instead, he could take the No.6 shirt, which has been unused at Arsenal since Laurent Koscielny left.
The No.5 shirt could also become available if Sokratis Papasthopolous who has been linked with Napoli leaves.
Other players are being linked with exits including No.15 Ainsley Maitland-Niles, No.20 Shkodran Mustafi and No.16 Rob Holding.