The Brazil international is widely expected to get his dream move to Camp Nou in the coming weeks, having seen the Catalan giants fail with three bids during the summer.
No confirmation of a fee being agreed has yet been given by either club, but Nike has offered a big indication that the transfer is close to going through after making a blunder on its website.
An image advertising custom shirts containing Coutinho's name was uploaded on the site, under the headline 'Where the magic happens', before quickly being removed.
"Philippe Coutinho is ready to light up Camp Nou," a caption accompanying the image read. "Get your 2017-18 FC Barcelona kit with the Magician's name on it. Act fast - free personalisation only available until January 6."
Spanish publication Sport suggests that talks will conclude as early as January 3, two days after the window opens for business.