Nasri converted two penalties in extra-time before Andrei Arshavin rounded off Arsenal's 4-1 win.
But Redknapp believes Nasri threw himself to the ground under pressure from Sebastien Bassong to win Arsenal's first spot-kick, from which they took the lead at 2-1.
"I thought the first one was harsh. He fell over. Really I think he dived for the first penalty," he said.
Bassong was also adamant that his challenge did not warrant a penalty.
"I didn't think it was a penalty," the former Newcastle United defender said in the Mirror. "He told me afterwards that I just barely touched him.
"It leaves a bad taste in my mouth because in extra-time I thought we could have achieved something. I did not touch him, I did not grab him. I have seen the video and from my point of view it was not a penalty. I touched his chest but I did not grab him. He went down too easily.
"It's gone but it's a shame the game turned on that moment. We all worked hard so to concede a second goal like this was hard to take.”
Arsenal manager Arsene Wenger had to watch the match from the stands, having accepted a charge and fine by the Football Association following his actions at the end of their 1-1 draw with Sunderland at the weekend.
By Luke Nicholls
