Arsene Wenger concedes it will be strange to face-off against Alexis Sanchez on Sunday when the Chile international steps out for Manchester United at home to Arsenal.
Alexis made the switch from north London to Old Trafford in January, in a deal that saw Henrikh Mkhitaryan move the other way, and is set to tackle his former team-mates for the first time this weekend.
Wenger brought Sanchez to Emirates Stadium from Barcelona in 2014 but Arsenal were unable to agree to a new contract with the 29-year-old, forcing the Gunners into a mid-season sale amid anger from fans.
Sanchez was amongst those who paid tribute to Wenger following the announcement he will leave Arsenal this summer, bringing an end to a historic 22-year spell with the club, and the French boss feels it will be unusual to come up against his former star forward.
"Of course [it will be a little bit strange to face Alexis]. The only thing that has not changed is the colour, that's still red," Wenger told Arsenal's official website.
"It's strange for me to see him in a different shirt because he had a strong bond with the club and of course he was here for a few years. He did extremely well for us."
The two-time FA Cup winner has since scored three goals for Manchester United, including an equaliser in the 2-1 FA Cup semi-final victory over Tottenham last weekend.
"At the time he did not accept our contract offer and the best possible way we could get something from his departure was to make an exchange for a player of the quality of Mkhitaryan," Wenger added.
"For him, it was a move to another big club. Overall, both parties had [the] interest to do what happened."