The Gunners set up a FA Cup semi-final tie against Bradford City at Wembley after defender Nacho Monreal and former Red Devils striker Danny Welbeck scored in a 2-1 win against Louis van Gaal’s side at Old Trafford.
Arsenal striker Sanchez, who is set to line up for Chile against Brazil at The Emirates on 29 March, praised the “genuine spirit” that the north London side showed against the 20-time English champions.
“It was a very physically demanding game, a box to box one,” Sanchez told Arsenal Player.
“I got back home both happy and exhausted. The team played the game with a great attitude and with a genuine spirit to win it from the very first minute.
“We never put our head down against a top club like Manchester United. That attitude gave us the victory.”
The 26-year-old has been a big hit at the north London club and in the Premier League thanks to a return of 13 goals in 25 top-flight games.
And the South American admitted that the Premier League is more intense than La Liga after having completed his big-money switch to The Emirates from Spain last July.
“It is indeed. Every team is really strong. For instance, you cannot take for granted any in-game score in this league,” Sanchez added.
“Any team can score goals in the last minutes of the game. I like that.”
Brazil v Chile is on March 29 at 3pm at the Emirates Stadium in London. Tickets are on sale at arsenal.com/tickets
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