Signing Sanchez is being viewed as a real statement by United, like Eric Cantona joined in 1992 and Robin van Persie - who also arrived from Arsenal - in 2012.
Mkhitaryan told the Arsenal website he had "always dreamed of playing for Arsenal". "Two trophies last season, progression on the field, we are getting better and stronger, I don't see any reason why not (give him an extension)?"
Sanchez, who nearly ended up joining Premier League leaders and United rivals Manchester City in the summer transfer window will be wearing the special number 7 jersey which has been donned by United charismatic players including the likes of Eric Contana, David Beckham, PSG winger Di Maria and current Real Madrid talisman Cristiano Ronaldo.
City came close to signing Sanchez in August and looked to be the favorites to get him this month, only to end their interest in the forward following a rival bid from United.
Arsenal boss Arsene Wenger believes that Manchester United new number seven only agreed a deal with the Red Devils because of the money since it could be his last bumper contract.
Sanchez had joined Arsenal in 2014 for £31.7 million after three years at Barcelona.
"Now that I'm here, I'll do my best for this club to create history". "I am very proud to be the first Chilean player ever to play for United's first team and I hope I can show our fans all around the world why the club wanted to bring me here". "He is a player that we will not forget, especially for his contribution to our Europa League victory".
Chile forward Sanchez, 29, who nearly joined Manchester City last summer, has signed a four-and-a-half-year deal worth £14m a year after tax.
Recently Arsenal has been also chasing Henrikh's former Borussia Dortmund team mate Pierre-Emerick Aubameyang, and reports are beginning to emerge that the Gunners have agreed personal terms with the striker but no fee has been finalized as yet.