Manchester United and Manchester City are tracking Wolves midfielder Ruben Neves.
The Sun says if the City chief Pep Guardiola does decide to make a move for the £60million-rated midfielder when the window opens, Jose Mourinho is ready to go head to head.
Mourinho is a big admirer and has followed Neves' progress closely, but he was willing to wait and see how he coped with the Premier League before making a move next summer.
Those plans could now be brought forward six months, with City insiders convinced Guardiola will make a bid in January after missing out to Chelsea on Jorginho in July.
That would see a repeat of last winter's battle between them for Alexis Sanchez, who eventually joined United.