The writing was on the wall for Alexis Sanchez at Manchester United in March, long before his loan to Inter was confirmed on Thursday evening.

In the aftermath of Ole Gunnar Solskjaer's appointment as permanent manager, club chiefs were privately insisting that the rug would not be pulled from under him with the sale of Paul Pogba to Real Madrid. In reply to questions about whether the French midfielder would leave, the answer was always a firm "no."

But when it came to Sanchez, the tone was very different. It was made clear even then that any decision on Sanchez's future would be left to Solskjaer. The club officials who had worked so hard to pinch the Chile international forward from under the noses of Manchester City 14 months earlier, acquiring him from Arsenal in exchange for Henrikh Mkhitaryan, had already given up.

The stats make for disastrous reading. Sanchez scored five goals in 45 games for United and just three in the Premier League over 18 months with the club. His last goal came in the FA Cup, at former club Arsenal in January. His last 90 minutes for his club came on the opening day of last season. It is slim pickings for a player being paid £391,000 a week, rising to more than £500,000 a week with associated bonuses.

The reasons why a good footballer has been so bad at Old Trafford are, as Jose Mourinho put it privately, "a mystery." At Barcelona, Sanchez averaged a goal every three games. At Arsenal, one in two. At United, it was one in every nine.

Some backroom staff put it down to a crisis of confidence not helped by a series of niggling injuries while others are of the opinion that the move was ill thought-out and, because of that, it was doomed to fail.

In the summer of 2017, Mourinho wanted Ivan Perisic to fulfill his wide forward needs and was left frustrated that, after Inter Milan set the price at £48 million, the United-owning Glazer family would only sanction opening bids of £22m, £23m and £24m.

It was in stark contrast to the way United pursued Sanchez during the January transfer window having sniffed a chance to get one over on City. They made him the highest-paid player in the Premier League, a decision Mourinho grew to feel was as much down to his ability to sell shirts as anything else. Perisic did not have the same star quality and Mourinho felt that balance on the pitch had been compromised for what United's commercial department believed was a better fit off it.

"Alexis Sanchez has set a new January signing record in terms of shirt sales, three times the previous record," executive vice-chairman Ed Woodward said in a conference call with investors. "This trade generated some interesting social media stats. It was the biggest United post on Instagram with 2 million likes and comments, the most shared United Facebook post ever, the most retweeted United post ever."

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Sanchez's arrival also impacted the harmony in the dressing room. Anthony Martial had scored in three consecutive Premier League appearances before the deal with Arsenal was agreed but was then immediately cast to the side. In the final four months of the 2017-18 season, Martial started just four league games and missed out on a place in France's victorious World Cup squad as a result.

There were problems off the pitch, too, after Sanchez's salary blew apart the wage structure. During David De Gea's contract negotiations the Spaniard questioned why he was being offered significantly lower terms despite being the club's player of the year in four out of five seasons between 2014 and 2018.

Approaching the end of his contract, Ander Herrera's demands were impacted, in part, by a realisation that Sanchez was earning upwards of £300,000 a week more. The Spanish midfielder ultimately opted to join Paris Saint-Germain when his deal with United expired.

One senior player, who is due to begin renewal talks in the coming year, has admitted privately that his agent doesn't know where to start with negotiations because the rules on acceptable figures have been re-written.

Wherever he has played, Sanchez has never served as the life and soul of the dressing room. But toward the end of last season, he had become so distant from the rest of the squad that some of his teammates told coaching staff they were worried.

Sanchez took exception at being asked to do an interview alongside Herrera, because he felt it was because the club did not trust him to do it alone. His closest friend at United was Romelu Lukaku and Sanchez's mood plummeted further when the Belgian was sold to Inter.

A week ago, Solskjaer suggested in a news conference that Sanchez could play a key role this season, but there were already mounting concerns that the situation had reached the point of no return.

It says everything about how far Sanchez's relationship with the club has deteriorated that United have agreed to pay £6m of his salary over the next 10 months to have him play somewhere else, and with no ability to bring in a replacement until January.

United's forward line is thin -- no one in the squad has ever scored more than 12 Premier League goals in a season -- and a team that was already struggling for goals has been depleted even further. And yet there is still a feeling within the club they are better off without Sanchez.

Sanchez will still have two years left on his United contract when his Inter loan ends, but he looks to have no future at Old Trafford. A transfer that seemed certain to be successful has turned into one of the worst in United's history and it will be some time before the club finishes paying the price.