The German bagged his first goal of the season in the 4-0 victory.
Keown has long been critical of the club's highest earner, but the former England international was pleasantly surprised by Ozil's showing at the Emirates.
"Whatever was said at half-time had an effect. The first half was quite poor but the second half was so free in the way that they played," Keown told BBC Sport.
"The shackles came off, they played with more confidence.
"Ozil, I thought his movement was really important, there was running off the ball with Aubameyang and Pepe was told that in the second half he needs to get at his opponent, which he didn't do in the first half.
"It was great to watch. It may have flattered them a little bit, 4-0, but Saka is a player going from strength to strength.
"Ozil was magnificent and Saka just keeps getting better and better.
"Ozil had much more purpose in his play and he gets his reward, fortunate with the finish but he deserved that goal.
"He's playing centrally, he wants to be that player who threads things together and it's really going well for him.
"Two wins from the last eight, we all know as Arsenal fans that they have been playing better than those statistics suggest, but today did."