The 21-year old has been a revelation in central midfield but could leave Spurs light at the back.
His defensive instincts have allowed midfield partner Ryan Mason the freedom to effect the game further up the pitch, and Mauricio Pochettino’s decision to trial him there is proving to be one of his best as Spurs boss.
Despite that, his change of position means Tottenham are now one central defender down – and this could be an issue.
Left-sided central defence is taken care of, with Kevin Wimmer likely to make his competitive debut in place of Jan Vertonghen in Thursday’s Europa League clash with Qarabag FK, but back-up for the right-sided Toby Alderweireld is less forthcoming.
Dier would have been the usual stand-in, but his new role as first-choice central midfielder means he will be rested alongside the Belgian duo, leaving Pochettino with something of a headache.
Federico Fazio is the clear option, but the Argentine has yet to make the squad this season and is the one player left at the club who doesn’t fit Pochettino’s system, after this summer’s clear-out.
Spurs were happy to let the giant defender go, but his move to West Bromwich Albion fell through at the last minute - as reported by the Guardian - and he remains on the fringes at White Hart Lane.
The club’s willingness to move him on suggests that Pochettino could look to the academy to provide cover for Alderweireld.
Cameron Carter-Vickers and Milos Veljkovic would be the two obvious candidates, but they are yet to be seriously involved with the first-team and throwing them into the deep end in two days’ time would be a surprise.
Fazio’s inclusion is therefore the more probable course of action and while the 28-year old has certainly put in some solid displays for Spurs, he remains ill-suited to Pochettino’s system and that will be a cause for concern.