Ramsey broke his leg that day at the Britannia Stadium, halting the momentum of his upwardly mobile young career.
But the 22-year-old midfielder will face Stoke again this Sunday at the Emirates on the crest of a wave, having scored against Marseille in midweek to make it six goals in seven games this term.
Asked about Ramsey's injury, Wenger said: "It took him a long time to get completely over that, especially in duels, in fights (for the ball).
"He was resistant to go into the fights for a long, long time but now he's over it.
"He had a difficult period last season where people became a little bit impatient with him. He lost confidence and sometimes, if you give the players a little rest, it can rebuild their confidence.
"They can think about their game and come back stronger and that's what happened to him.
"As for the rest, he scores goals now. I always thought he would score goals if he improved his technical quality.
"When you watched the games, you saw him always in good positions in the box. When he got the chances he missed sometimes but he has improved tremendously on that.
"He has a great engine, a great spirit and has an obsession, he always wants to be better. That is, of course, a very good ingredient."
Ramsey may be joined in the midfield at some point on Sunday by Mikel Arteta, who could return to the squad after being sidelined by a torn quadricep.
Wenger said of Arteta: "He is a leader, we are happy to have him back."
Arsenal v Stoke is live on Sky Sports 1 on Sunday at 13.30.