Arsenal manager Arsene Wenger has supported Alexis Sanchez's assertion that he "always gave 100%" to the club.
Sanchez wrote a long post on social media after leaving Emirates Stadium to join Manchester United, with Henrikh Mkhitaryan moving the other way.
The Chile forward, 29, also said that former players spoke "with no knowledge of what happens inside the club and caused damage".
"Sanchez is a great guy and he has always been committed," said Wenger.
- How did Sanchez end up at Man Utd? And will he fit in?
- Sanchez v Mkhitaryan in stats - shooting, scoring, passing and assists
Last month, former Arsenal striker Ian Wright said on BBC Radio 5 live it looked as though Sanchez, whose Arsenal contract was set to expire at the end of this season, had "clocked off" and was "not putting in a shift" after almost joining Manchester City last August.
Sanchez has scored seven Premier League goals in 19 matches at a rate of 0.37 per game this season, compared to last term's contribution of 24 goals in 38 matches at 0.63 per game.
Meanwhile, Armenia captain Mkhitaryan has made only 10 top-flight starts this season and, as reported by the BBC, it is understood there was a breakdown in trust between him and United manager Jose Mourinho.
Wenger said: "I believe we lose a world-class player and gain a world-class player. Overall, I think Mkhitaryan has the qualities to integrate into our game. He has a good team attitude as well. I'm confident it will work."
Chilean's eye-watering numbers 'important'
Sanchez has signed a four-and-a-half-year deal worth £14m a year after tax at Old Trafford and will wear the number seven shirt.
He will reportedly earn £350,000 a week at United and this will will rise to £450,000 when his image rights are added in, and £600,000 including bonuses.
He is available for United's FA Cup fourth-round tie at Yeovil Town on Friday, which will be shown live on BBC One from 19:30 GMT.
"He is 29 years old, it is maybe his last contract," said Wenger. "Financially it is important. He is going to a great club. You can understand why, for a professional player, you want to combine both aspects."
Any more incomings?
The arrival of Mkhitaryan in a swap deal is Arsenal's second signing of the January transfer window, having brought in defender Konstantinos Mavropanos from Greek side PAS Giannina for an undisclosed fee.
The club are in talks to sign Borussia Dortmund striker Pierre-Emerick Aubameyang, but the Bundesliga side say the player will cost in excess of £50m.
Asked whether he was confident of landing the Gabon international, Wenger replied: "Confident, I don't know. At the moment, we are not close to doing any deals with him or anybody else.
"You never know how close you are. At the moment it's one of the possible movements. The final decision is not made.
"We have other things in mind as well, plenty of opportunities and different positions in mind."
Any more outgoings?
Including Sanchez, three experienced players have left Emirates Stadium this month with forward Theo Walcott joining Everton and midfielder Francis Coquelin signing for Valencia.
"No, I'm not worried about that," said Wenger when asked about how the Sanchez departure will effect Arsenal's status in the game.
"When players get to a certain age and want to go you have to respect that. We are a serious football club with prospects and we will spend what we can afford."
Striker Danny Welbeck has been linked with a transfer to Turkish club Besiktas but Wenger said he "wants Danny to stay here".