The Chilean forward is preparing for a return to familiar surroundings in fourth-round action.
The Red Devils are due in north London on Friday for an anxiously foreseen tie between two arch-rivals and Premier League top-four hopefuls.
Manchester United will make the trip floated by a run of seven successive triumphs under Solskjaer.
Sanchez has had little influence in that record-breaking sequence after nursing a series of niggling knocks, but is ready to step back into the fold and touch off his United career against a former club.
Ex-Arsenal defender Keown told the Daily Mail of the threat posed by a man who has danger presented by a man who has persevered through a troublesome time since moving to Old Trafford in January 2018: “Ole Gunnar Solskjaer has been waiting for the perfect moment to re-introduce Alexis Sanchez.
“What better opportunity for the forward to relaunch his Manchester United career than by going back to his old club and knocking them out of the FA Cup?
“Not only will he be desperate to prove a point to the Arsenal fans, but Sanchez gets a real buzz from playing in this competition.
“He has scored in two FA Cup final victories with Arsenal and found the net in three semi-finals — including for United against Tottenham last season.
“He could cause Arsenal serious problems down their left flank. Sead Kolasinac plays as more of a wing-back than a defender, often leaving gaping holes behind him.
“Those are the kind of spaces Sanchez will be looking to exploit to destroy Arsenal’s FA Cup dream. This is a player who needs the love of his manager.
“Solskjaer has been talking him up in recent weeks as if readying him for this huge clash at the Emirates.”
Sanchez won’t be the only attacking star to feature at Emirates Stadium, with Keown expecting an entertaining encounter between two sides brimming of confidence.
“I’m hoping for a thrilling contest that ends 3-2… and I believe Arsenal’s firepower will be enough to inflict a first defeat on Solskjaer.”