The Newcastle squad are currently in Spain as part of their pre-season, but preparations under new manager Matthias Jaissle have been dealt a significant blow.
Per The Athletic, Hall, 21, has returned to Tyneside earlier than expected, alongside teammates Fabian Schar and Lewis Miley.
All three players are set to miss Saturday evening’s friendly against Valencia in Spain, which marks Jaissle’s first official game in charge since taking over from Eddie Howe.
Newcastle insists it’s due to a minor fitness issue, but it comes at a time speculation is mounting over interest from Man United.
Having already lost Anthony Gordon, Sandro Tonali, and Bruno Guimaraes, Newcastle are adamant they won’t sell any more key players.
Hall isn’t expected to be sidelined for too long and could even feature in Wednesday’s friendly against Everton at Murrayfield in Edinburgh.