Sanchez joined United from Arsenal in a swap deal involving Red Devils outcast Henrikh Mkhitaryan on Monday, but Belgium worldwide De Bruyne explained that City would move on from the saga and not let it affect them.
Speaking at his news conference earlier on Thursday - before his new contract was announced - Mourinho hailed the club's recent signing of Alexis Sanchez from Arsenal.
Take a look through the gallery above to see all the best tweets as fans react to Mourinho's latest comments about Alexis Sanchez! I saw him play in different systems, I saw him successful in every country.
"He's a player who becomes more than a player, and because of that motivation I think he can play in four different positions". You can not do that with 11 players, so the players at big clubs know that the squad is made of 20-something players where everybody wants to play and where there is space for everybody.
Diego Forlan, one of 15 South Americans to have played for the Red Devils, is excited for Sanchez.
"I would like to say a big thank you to the owners and to Mr (Ed) Woodward for the recognition of my hard work and dedication".
"We've got one of the best attacking players in the world".
'I believe that at this club it's possible to achieve anything.
City won't lose sleep over one transfer, however, and now lie 12 points ahead of their city rivals at the summit of the Premier League after 24 matches. Because of the way they play.
United's young trio of attackers, Jesse Lingard, Anthony Martial and Marcus Rashford, have combined to add 20 goals in the league this season as they remain second in the standings, 12 points behind runaway leaders Manchester City.
"Could he have performed better for us?" I know him very well for many years.
In the first half we gave them too much respect and we were a bit scared to really go for it, and we suffered from that, said Wenger. Maybe. But I don't think regrets.
The striker said on Monday that he could not turn down the chance to work with United manager Jose Mourinho.
Other than Sir Alex Ferguson and Sir Matt Busby, who spent almost 27 and 24 years in charge respectively, United's longest serving post-war manager is Ron Atkinson, who was manager for five years and five months before making way for Ferguson in October 1986.