Tottenham manager Pochettino is now the favourite to replace Mourinho if the Portuguese boss leaves.
With Man City running away with the league last season and Liverpool strengthening considerably over the summer, challenging for the title will be hard, as will playing a style of football that will entertain the fans after 2017/18's dour displays.
The Red Devils have snapped-up third-choice goalkeeper Lee Grant, young full-back Diogo Dalot and midfielder Fred but the Brazilian worldwide is the only one of the new recruits expected to be a first team regular this season so Mourinho is keen to further strengthen his ranks.
United's senior players, including £52 million summer signing Fred, Sanchez and Juan Mata were in one group, but their effort was minimal and passes were frequently intercepted or went astray.
United have made three signings this summer, with Mourinho wanting a further two before the August 9 transfer deadline, but fearing he may only manage one - a grim scenario with his squad already severely depleted.
Despite not being involved in United's pre-season fixtures, Dalot is enjoying his experiences with the Red Devils so far. "If it's possible, it's good, if not then we keep fighting and working and believing in the players that we have".
Rangers Trade Cole Hamels To Cubs
Butler, a former first-round pick, has made 39 career starts with Colorado and the Cubs , compiling a 10-18 record and 5.65 ERA. Hamels played for the Phillies for almost ten seasons until being traded to the Rangers in the middle of the 2015 season.
"In his age group, he is the best full-back in Europe and we all believe he has a bright future ahead of him at Manchester United", he said.
Brazilian midfielder Fred is expected to be thrust into the starting XI, but Mourinho has said that the team "is not going to be very different" from the one that ended the 2017-18 season.
To add to their woes, the gaffer has revealed that he faces a lengthy injury list to add to his missing big-name players recuperating from a taxing World Cup campaign.
"We start the game with nearly half the players who are not even going to belong to our squad on August 9 [transfer deadline day]". "We are not playing here to improve the team, the dynamic or our routines".
"I agree totally with the window closing at the same time as the Premier League starts".
"I agree that when the season starts the transfer window closes", said Mourinho. Honestly, I'm waiting. If I stay, I stay and I do what I did up until now.