Manchester United boss Louis van Gaal is keen to strengthen his inexperienced back four and a move for the Belgian international has been on the cards all summer.
Vermaelen returns to north London this week to begin pre-season after the World Cup but could be straight on a plane up to Manchester to complete his move to Old Trafford.
The 28-year-old has fallen down the pecking order at the Emirates and is now back-up to the first choice centre backs, leaving a defender at the prime of his career sitting on the bench.
Wenger has admitted that his captain may well leave and if he does, a replacement will be found.
“I cannot guarantee he will stay, but should he go I would bring another centre-back in for sure,” Wenger said after a pre-season win over Boreham Wood.
United lost both Nemanja Vidic and Rio Ferdinand over the summer with Patrice Evra set to follow suit.