Fabregas, now at Chelsea, finally revealed after years of guessing that he launched pizza at the then-Manchester United manager following a fiery clash between the Red Devils and Arsenal in October 2004.
Ferguson had said after the incident he hadn't seen who had struck him in the face with the pizza missile but, for years, Fabregas was the person thought responsible particularly after Keown had hinted at it during an interview with BBC 5Live in 2011.
But following his admission about pizzagate in an episode of A League Of Their Own, which will be aired on Thursday, Fabregas said Keown couldn't have known it was him because the former defender was standing in the Old Trafford players' tunnel "just, like, punching people".
Keown has now revealed that he did not see the incident - because he had already left the Gunners for Leicester earlier that year - but wishes he had.
Writing in his column in the Mail, the 51-year-old said: "Sorry Cesc, I wasn’t at Old Trafford when you flung the pizza at Sir Alex Ferguson... but I wish I had been!
"Often memories of these titanic clashes merge into one. Maybe he assumed that because there was a melee I must have been there, but I had already left Arsenal for Leicester."
He added on that match which United won 2-0: "In these games, you could not afford to get embroiled in personal vendettas. But with such strong-willed individuals on both sides it was inevitable that tempers would flare.
"In the 801 games I played for club and country I only saw punches thrown in the tunnel on two or three occasions — and one of them was during a game between Arsenal and United.
"But when I look back, there was always a level of respect between us."