Ole Gunnar Solskjaer's success in performing a "cultural reset" at Manchester United was a central factor in the club's decision to hand him a three-year contract as permanent manager, sources have told ESPN FC, following confirmation of the Norwegian's elevation to the top job at Old Trafford on Thursday.

Solskjaer was drafted in as the caretaker manager in December following the sacking of Jose Mourinho, with United's owners, the Glazer family, and executive vice chairman Ed Woodward turning to the club's former striker amid growing concern over both results and squad morale under the former Chelsea and Real Madrid coach.

While Solskjaer was initially regarded by the Glazers and Woodward as a stopgap appointment with only an outside chance of becoming the club's full-time manager, ESPN FC can reveal that the 46-year-old became the front-runner for the job as early as mid-January, following a 1-0 win at Tottenham, with an immediate uplift on and off the pitch prompting United to halt plans to seek out a more high-profile appointment.

But with Solskjaer now having been given the green light to reshape the squad this summer ahead of an anticipated challenge for the Premier League title next season, ESPN FC has been told that alarm bells with Mourinho began to ring during last July's preseason tour of the United States, and that the full impact of Solskjaer's job to date can be fully judged only through the prism of his predecessor's final months in charge.

Ole Gunnar Solskjaer was named permanent Manchester United manager on Thursday. Oli Scarff/AFP/Getty Images

Solskjaer inherited a squad that had grown restless under Mourinho, with leading figures such as Paul Pogba dropped and openly criticised by the Portuguese manager. After losing 3-1 at Liverpool in Mourinho's final game in charge on Dec. 16, United were in sixth position, 11 points adrift of fourth place and a Champions League berth. And despite handing Mourinho a new contract just 11 months earlier, the deteriorating mood within the club, combined with results on the pitch, prompted the Glazers and Woodward to sack the man they had initially appointed in June 2016 as being the one to deliver the Premier League title back to Old Trafford.

Sources have told ESPN FC that Mourinho's barbed comments, following a friendly defeat against Liverpool in Ann Arbor, Michigan, in July, about Alexis Sanchez not being happy with the players he was playing alongside, confirmed fears that the manager was embarking on the troubled "third-season syndrome" that has been a fault line throughout his coaching career. Mourinho's demeanour and the atmosphere within Old Trafford continued to nose-dive during the early weeks and months of the season, culminating in his dismissal 48 hours after the 3-1 defeat at Anfield.

-- The inside story of how Jose Mourinho unravelled at Man United

Solskjaer's arrival, after cancelling his contract as coach of Norwegian outfit Molde, was designed to restore a feel-good factor at the club, but while results immediately improved -- Solskjaer won his first eight games in charge -- it was his impact behind the scenes that most impressed Woodward and the Glazers. The buzz-phrase within the club was of the need for a "cultural reset" -- bringing positivity back to Old Trafford, making players, fans and staff happy again and overseeing a return to United-style attacking football.

There was also a determination for Solskjaer to project a more positive message to the media than Mourinho, with the United hierarchy also wanting the team to quell disquiet among the supporters by displaying more flair. Sources have told ESPN FC that the immediate sight of players taking risks under Solskjaer and playing forward passes rather than sideways ones was another small, but crucial, tick in the caretaker manager's favour with the owners and Woodward.

But Solskjaer also won admirers in the boardroom by restoring discipline in a subtle, but noticeable, manner. Solskjaer's decision to turn back the clock to the Sir Alex Ferguson era by ordering players to wear club-crested suits for games, insisting on top buttons being fastened, ties worn and big headphones being left on the bus, impressed staff behind the scenes, as did his reminder to players to sign autographs for fans waiting outside the ground.

Senior figures at the club believed that Solskjaer had instantly created the environment for United to "be United again," but results on the pitch were ultimately the reason why initial interest in Tottenham manager Mauricio Pochettino was never followed through upon with an approach to the London club.

Under Woodward's leadership, United have tasked all managers with fulfilling their "three pillars of success," but none of David Moyes, Louis van Gaal or Mourinho has been able to do so. Those pillars -- winning, playing with an X factor and promoting youth -- have all been achieved by Solskjaer, however, leaving Woodward and the Glazers with the seemingly straightforward decision to hand him the job on a full-time basis.

Within Old Trafford, the suggestion that United might be repeating the mistake made by Chelsea in 2012 -- when Roberto di Matteo was given a permanent contract after winning the Champions League as caretaker boss -- has been given short shrift. Sources have told ESPN FC that the view within the club is that there is little comparison and that Solskjaer's appointment has been made while the team "are favourites to finish fifth" -- underlining the stance that the decision has been made by assessing the bigger picture and not just results on the pitch.

And rather than wait until the end of the season to confirm the appointment, as had originally been planned, the club chose to finalise the deal now in order to give Solskjaer and his coaches time to plan summer recruitment and strategy for next season. A technical director will be appointed before the end of the summer transfer window to work alongside Woodward and Solskjaer, and United believe that Solskjaer's personality and outlook has enabled them to fine-tune the job description of that role in contrast to Mourinho, who made it clear that he would not countenance working alongside such a figure.

But Solskjaer has changed the mood and the landscape at United. He has performed the cultural reset, but as he admitted in his news conference Thursday, this is when the hard work really begins.