Manchester United went into their Champions League tie with Paris Saint-Germain full of confidence.
Since Ole Gunnar Solskjaer took over from Jose Mourinho, United had been unbeaten and were playing some brilliant football.
And with PSG missing Neymar and Edinson Cavani ahead of their trip to Old Trafford, many fancied the Red Devils to win the first leg.
However, after a tight first-half, the match changed when Presnel Kimpembe turned in an Angel di Maria corner at the back post.
Speaking to the BBC ahead of United’s FA Cup clash against Chelsea, Sanchez explained how he realised United weren’t getting back into the tie as soon as PSG took the lead.
"When they [PSG] scored that first goal, I looked at them [team-mates] and I thought, no, something's not right,” Alexis said.
“I looked in their eyes and I thought, there isn't that feeling there [of coming back], I'm not getting it."
Sanchez's poor performance against PSG may have had something to do with the injury he picked up before he entered the fray.
Whilst warming-up, Sanchez colliding with the assistant referee and he's now admitted that he suffered bruising from the collision.
"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. Bang," he said.
"And I went back to the dugout and I said to [reserve goalkeeper] Sergio Romero: 'I've just been whacked and I'm about to go on'.
"I've got bruising but that's not an excuse for not being on my game in the way that I normally am."