Ryan Mason was expected to return for tomorrow's match with Manchester City, but has been ruled out.
The England international joins Mousa Dembele, Nabil Bentaleb and Alex Pritchard on the unavailable list, but his absence could prove to be a blessing in disguise for Tottenham Hotspur.
Alli (19) and Dier (21) aren’t the most experienced pair, and will face a tough task to win the midfield battle against City’s star-studded bunch.
Alli over Mason could leave Spurs more exposed, owing to his more adventurous nature, but bravery in attack and pace will be vital if the Lilywhites are to pick up anything from the game.
Mason has shown signs of his willingness to get forward recently - not least for his goal against Sunderland last week – but Alli is the more athletic of the two and is better suited to the box-to-box role.
The injuries to Bentaleb and Dembele have further accelerated Alli’s progress, and the former MK Dons man has been up to the task whenever he has been called upon.
The showdown with Manuel Pellegrini’s men will be his biggest test yet, but with Yaya Toure notoriously lax in his tracking of runners – the stage could be set for Tottenham’s latest young star to steal the show.