Sanchez is expected to swap north London for the north west in the coming days with Jose Mourinho's side willing to pay Arsenal's £35m asking price for the Chilean, whose contract with the Gunners expires at the end of the season, but they were hoping to include Mkhitaryan in the prospective deal.
Mkhitaryan has felt the ire of United manager Jose Mourinho on more than one occasion since joining from Borussia Dortmund in the summer of 2016 and was omitted from his side's 3-0 win over Stoke City on Monday (15 January) by the Portuguese, who admitted his decision to exclude the 28-year-old from his match-day squad was not "a pure tactical decision".
Many took Mourinho's decision to exclude Mkhitaryan as a clear indication that he is set for pastures new, but his representative Raiola, who also acts as an agent for United stars Paul Pogba, Romelu Lukaku and Zlatan Ibrahimovic, was keen to stress that his client is still considering whether to join Arsenal, who are also looking to close deals for Pierre-Emerick Aubameyang and Bordeaux forward Malcom.
"Manchester United is not going to sign Sánchez unless Mkhi agrees to join Arsenal," Raiola told The Times. "Mkhi has not decided yet. Mkhi is going to do what is best for him. He has two-and-a-half years left on his contract, so it's his decision."
"Sánchez is part of the Mkhi deal, not the other way around."
Sanchez was widely expected to join United's arch-rivals Manchester City and seemingly had his heart set on a reunion with Pep Guardiola, whom he worked with while at Barcelona. But City eventually withdrew their interest in the 29-year-old due to the ever-increasing cost of the prospective deal - Sanchez's camp are looking to strike an agreement which would see the forward earn £18m-a-year.
Chelsea have also reportedly made a late move to sign Sanchez but United are still in pole position despite Raiola's comments over Mkhitaryan, who may not be the only playmaker to leave Old Trafford this month; Juan Mata is now able to negotiate with foreign clubs regarding a potential free transfer in the summer.
United have not yet activated their option to extend the Spaniard's contract by another 12 months, leaving Mata with the ability to talk to clubs from overseas. Mourinho's men are expected to extend the 29-year-old's contract in the coming weeks, while the former Chelsea boss is also willing to let young defender Axel Tuanzebe go on loan until the end of the season. Aston Villa are said to be interested in the Tuanzebe, who has made one substitute appearance in the Premier League this season.