Jose Mourinho believes Manchester United and Arsenal both get a "fantastic deal" in swapping Alexis Sanchez and Henrikh Mkhitaryan.
United's rivals Manchester City had tried to sign Sanchez in the summer and revisited the possibility in this window only to pull out due to the rising costs.
Arsenal wanted £35million for a player out of contract in the summer and United's willingness to meet Sanchez's wage demands and use a makeweight in Mkhitaryan, who is valued at the Gunners' asking price, allowed a straight swap to take place.
"United and Arsenal made a fantastic deal, I lost a fantastic player, Mr Wenger lost a fantastic player.
In Pictures | Alexis Sanchez joins Manchester United | 22/01/2018
"Alexis changed from a fantastic club to a giant club and Mkhi changed also for a fantastic club, so it was a great deal for everybody.".
Mkhitaryan was a target for Arsenal before he moved to United in the summer of 2016 but he did not settle into the side and was often left on the sidelines by Mourinho.
Now he has a chance to reinvigorate his stalled career in north London, and Arsene Wenger has backed the 29-year-old to do so following his challenging time with the Red Devils.
"Yes, of course you worry about how much it has affected him," he said on Tuesday.
"But as well but it's a new chance for him, what you want in life is a new chance and I'm sure with his quality that he will take it. I met him at the time (he moved to United), at the time we were close but in the end it didn't work."
In Pictures | Henrikh Mkhitaryan's first training session at Arsenal
Wenger insists he can incorporate Mkhitaryan, as well as another potential new recruit in Borussia Dortmund striker Pierre-Emerick Aubameyang, into his squad as players will have to accept they cannot play every week.
"Some people need confidence and to feel security," he said.
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"But in football teams, there is a number (of players in a squad) that pushes you, a number that makes you asleep, and a number that paralyses you.
In Pictures | Henrikh Mkhitaryan joins Arsenal | 22/01/2018
"So you have to find the right number in each squad to give fair competition, but as well not be too much in administration, and not to have no chance at all - no matter what happens - to play.
"Some will have to be in and out. But on the other hand, we have seen that (Aaron) Ramsey has been out injured many times, Jack Wilshere as well.
"We play in many competitions and you have a number you can fit in."
Additional reporting by the Press Association.