To say Celtic's dip in form this season has been alarming would be an understatement. 

Way off the pace in the title race, consecutive 4-1 losses against Sparta Prague saw them crash out of the Europa League in miserable fashion, with the pressure ramped up on manager Neil Lennon. 

As if that wasn't bad enough, reports surfacing out of Italy suggest one of their key players is a target for one of Europe's major clubs. 

Back in September, Lennon spoke of how he had a private meeting with Kristoffer Ajer amid suggestions other clubs were keen to sign the central defender. 

Largely an ever-present this season, the 22-year-old has won the most tackles (15) and made the most interceptions (18) of any Celtic player in the league according to FBRef. 

So, it's fair to say the Norway international is a crucial part of the set-up. With the defence proving far from convincing this season, it's scary to think where the champions may have been without him. 

Well, perhaps that won't be just a scary notion much longer. 

According to Calcio Mercato, Italian giants AC Milan are keen to sign him as they sit atop Serie A once again and will offer Diego Laxalt as a potential swap. 

Given how poorly Celtic have played this season and the loss of prize money through not qualifying for the Champions League, it'd surely be hard to stop a resurgent Milan tempting one of their key players away. 

A bad situation for Celtic could be about to get worse in January.