United remain locked in negotiations with Leicester over a potential deal that could see Maguire become the most expensive defender in history at £80m.
The Daily Mail reports that Maguire called his employers on Monday morning and spoke with the club doctor, before it was agreed that he could spend the day at home.
There is no suggestion that there is anything underhand with regard to his future and it is specifically pointed out that this is the first day of pre-season that Maguire has missed since reporting for duty earlier this month following his summer holiday.
Leicester manager Brendan Rodgers has publicly praised Maguire's attitude on more than one occasion this summer and the 26-year-old has played in all of the club's pre-season games.
But it won't stop people from trying to connect the dots and make his illness about a transfer.
The Metro, for example, came up with the following headline: 'Harry Maguire misses Leicester City training as Ed Woodward looks to close £80m Manchester United transfer', and declined to actually mention the reason why until the article's fifth paragraph.
Even Sky Sports ran with a sensationalised headline - 'Harry Maguire misses Leicester training amid Manchester United interest' - seeking to initially hide the true cause of his absence. Both talkSPORT and the Daily Express opted against mentioning illness at all in live blog entries.
The most recent update in the ongoing saga explained that Leicester are asking for a higher percentage of the overall £80m fee to be paid up front. That is apparently as a result of the Foxes being unconvinced United will trigger various performance-related add-ons.
If Maguire is to complete the switch to Old Trafford, time is of the essence. There are now less than two weeks until the Premier League transfer deadline on 8 August and Leicester would also need time of their own to secure a replacement if the deal does go through.