The Chile international completed a move to Manchester United in a swap deal that saw Henrikh Mkhitaryan seal a switch to Arsenal earlier this week.
Sanchez was Arsenal’s top goal-scorer in the last three seasons after the 29-year-old netted 80 goals in 165 games in all competitions.
The South American established himself as one of the Premier League’s best players at Arsenal alongside talents such as Kevin De Bruyne, Hazard, Harry Kane and Paul Pogba.
While Arsenal have managed to add Mkhitaryan to their ranks as part of the deal, Sanchez will leave a void in Arsene Wenger’s team given his ability to score goals and create chances.
Speaking ahead of Chelsea’s trip to north London for the second leg of the Carabao Cup semi-final, Willian delivered his verdict on Sanchez’s exit from Arsenal.
“To lose this kind of player is not easy,” Willian told the Evening Standard. “It would be like losing Eden here – he is a great player.
“Is he that important to them? Of course. No one wants to lose this kind of player.
“They are two great players but [unlike Sanchez] Eden is still here. Great players have quality to play in matches like this.
“Arsenal have other players but Sanchez is special.”
Arsenal have been heavily linked with a move to sign Borussia Dortmund striker Pierre-Emerick Aubameyang in the January transfer market.
The Gunners are in sixth place in the Premier League table but five points adrift of Liverpool FC, who occupy the final Champions League qualifying spot.
The north London side will take on Swansea City at the Liberty Stadium in their next Premier League game.
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