The Chile worldwide remains down in the dumps over at Old Trafford having scored just two goals all seasons.
"It's one of those things".
And Sanchez admits that he should have done more for the club since his arrival 13 months ago.
"For the quality he possesses as a player, he works as hard as anyone, but I don't see that anymore".
"I'm a player that, if I'm not in contact with the ball, I lose that spark, and sometimes I want to play in every game".
Sanchez has played more than 700 games for club and country since making his senior debut as a teenager, raising suggestions that he has already peaked and may not recapture the outstanding form he showed at Barcelona and Arsenal. "We are challenging to be top four, challenging against very, very good teams, so you need the players to step up now and you expect that at Manchester United at the end of the season".
"It's not an excuse because if I go on for 10, 20 minutes, I have to perform because that's what I'm here for, to make a difference".
Manchester United could have both Anthony Martial and Jesse Lingard back from injury in time to face Liverpool next weekend, despite previous estimations that the pair would miss two to three weeks of action.
"The referee's assistant, when we had a counter-attack, came flying down the line, and I had my foot there and he crashed into me".
Yet still, Sanchez says he looked at his teammates after Presnel Kimpembe opened the scoring and noticed a lack of belief that they could get back in the game.