The Independent's Miguel Delaney wrote that Mourinho has become frustrated with Bailly and is "fed up at how often he can't pick" the Ivory Coast international, who has been absent with several injuries this season.
The suggestion of a Bailly departure is sure to be met with derision by many of the club's supporters, who saw him rise to become the club's best central defender in a short space of time after his 2016 arrival.
His absence from the United starting XI in Saturday's FA Cup final against Chelsea was an indication of Mourinho's current mood toward the player, and Bleacher Report's Sam Pilger was left bemused:
The Special One is renowned for being a headstrong manager who likes to govern within his own house, and despite Bailly's injury troubles this season, the signs are there that not all is right between the pair at present.
Bailly, 24, missed eight matches in his first season at Old Trafford but was sidelined for 26 games this term, per Transfermarkt, as Marca's Chris Winterburn further explained an odd stand-off:
Metro cited Delaney's report and added it's Bailly's lack of willingness to "put his body on the line" that irks Mourinho, who was incensed when his player missed a fixture against West Bromwich Albion, only to report for training the next day.
Bailly's absence for the FA Cup final defeat to Chelsea also appeared to disprove Mourinho's earlier suggestion that it was 2018 FIFA World Cup hopefuls keeping him out of the line-up, per broadcaster Deji Faremi:
Deji Faremi @deejayfaremi
Mourinho:"Rojo, Lindelof, Jones, Smalling, all of them are wishing to make the squad. I try not to (make those sentimental decisions), but I still have space for a little bit of feelings so when I look to the other 4 CBs fighting for a position in the WC I am giving less to Eric”
Alderweireld is in a difficult situation of his own, with a Spurs contract that expires next summer and a release clause that will kick in then, making the 29-year-old available for only £25 million unless a new deal is agreed.
As good as Bailly is, it's not unthinkable that Mourinho would cut ties with a player on principle. James Ducker of the Telegraph illustrated the hit-and-miss nature of his recruitment at United thus far:
James Ducker @TelegraphDucker
Mourinho signings as #MUFC manager: Mkhitaryan (sold), Ibra (left), Bailly (frozen out), Lindelof (didn't make Cup final 18), Pogba (future v uncertain), Sanchez (playing like a drain), Lukaku (felt he could have done more to be fit for final), Matic (the one he's happy with)
According to Samuel Luckhurst of the Manchester Evening News, United are willing to pay £55 million for Alderweireld this summer, while Bailly would be expected to court more than the £30 million he arrived for two years ago from Villareal.
Casting away a player like Bailly seems like madness, injury troubles or not, but the idea of landing Alderweireld as a replacement could make such a departure that much smoother for the Red Devils.