The Gunners were shot down 3-1 by the Red Devils a fortnight ago, coming as a first defeat for the north Londoners at the Emirates Stadium this season.
Wenger’s men were then frustrated by the Saints this weekend as they had to come from an early goal down to salvage a 1-1 draw in the final minutes as Arsenal missed a big chance to take advantage of their top-four rivals’ dropped points.
“I felt that the Manchester United game played a bit of a part in the head of our defenders,” he said.
“It was a bit in their head and they were a bit apprehensive to start well again and that’s why it is sometimes not good to talk about the problem because you create a bigger one.
“I’m not happy with the point because I wanted three, but if you cannot win it, don’t lose it and we kept going.
“We were relentless, after a difficult start we were caught cold and overall it was a windy, rainy afternoon against a team who played well and were quick on the counter-attack.”