United pipped rivals Manchester City to the signature of Sanchez in January 2018 and made him the highest paid player in the English top-flight with a £315,000 (R5.5m) weekly salary, as per CNBC reports.
His arrival sparked major optimism as a world-class performer from Arsenal tipped to inspire The Red Devils back to their attacking glory days.
However, he struggled to gain form under former manager Jose Mourinho and his progression was often interrupted by niggling injuries before his below-par displays saw him dropped by the Portuguese tactician altogether.
Since Mourinho's exit, several of United's underperforming stars have seen the performance levels significantly improve, but the 30-year-old has not been one of those players - with his uninspired display against Leicester being scrutinised by the vast majority of United's supporters.
This has led club legend, Gary Neville, to believe that he is struggling to adapt to a new style of play, as his age no longer accounts for the explosive direct running that made him one of the most feared attackers in England.
That was a big audition for Alexis Sanchez today and he failed it miserably. A lot seem to be waiting for him to come good but he’s not showing anything. Don’t really see the point in persisting come summer.
— Alex Shaw (@AlexShawESPN) February 3, 2019
"He looks like he’s lost a little bit of his spark and his pace," said Neville on Sky Sports. "If that is the case, can he adapt his game?
"Can he get in behind still, face a man up, or become more of an assist player, a hold-up player? When a player loses that little bit of pace, he starts to drop in and move into areas where it’s easier to pick the ball up.
"He looked to me like a player who is doing the simple thing - drop, beat players with his back to the goal, and then lay it off, rather than turning directly on people.
Meanwhile, former Liverpool captain Jamie Carragher compared the 124-time capped Chile international to Torres, who sensationally flopped after a club-record move from The Reds to Chelsea.
"Under Mourinho, he would consistently lose possession," said the retired Liverpool defender. "He's got to do more himself.
"Looking at him in a Manchester United shirt was like looking at Fernando Torres in a Chelsea shirt. You see this blistering pace and power in one of the stars of the Premier League - but it just seemed to go.
"Does that go through a lack of confidence, the manager’s instructions, or the amount of football the lad has played? What he does for his country has maybe played a part. He has to go so far over there for games.
"And he’s consistently played football for a while now."
Sanchez has scored two goals and registered four assists in 17 games across all competitions this season.
