Wenger once sent Keown on a scouting mission to check the defender out, which he did.
But the north London club were worried about the centre-back's mobility, and ultimately decided against signing him.
Keown said: "Somebody asked me to take a look at him and I thought he was a decent player. They thought he was a big player, but was he going to be mobile enough?
"I think he's gone on to prove all the qualities he needs to be a top player."