Martin Keown has claimed that Arsenal should have retained the services of goalkeeper Emiliano Martinez.
At a time when Bernd Leno was sidelined with a knee injury, Martinez made a positive impression between the sticks, helping the Gunners win the FA Cup.
However, Mikel Arteta opted to recall Leno on his return to the squad, resulting in Martinez being allowed to join Aston Villa.
While the North London outfit put the funds towards making several high-profile additions, Keown has cast doubt over the decision after Leno struggled against Rapid Vienna on Thursday evening.
Speaking to BT Sport, Keown said: "Having let Martinez go, who was magnificent, to see Leno making these types of mistakes, you wonder whether it was the right call.
"It was a difficult night for Leno. The team had their backs to the wall but showed very good character to get back into it.
"A couple of changes were made. I thought when they changed it actually and went to a back five, the pictures then became more familiar to the players and they found a way to win this match."
Martinez has started in each of Villa's four successive wins in the Premier League this season.
