Gunners chief scout Steve Rowley was virtually a season ticket holder at Bolton Wanderers last season as he checked on the Derbyshire-born centre-half who made his full England debut in September 2010.
Cahill revealed: "I was aware he was watching me because people at the club would tell me. He certainly did his homework and he must know me inside out by now. If you watch a player over one or two games you might make an incorrect judgment. But after 30 games they either like you or they don't.
"When the England squad were training at London Colney, Arsene Wenger would come and watch us because we right on his doorstep.
"But the two clubs couldn't agree a fee and there wasn't anything I could do about that. I've no idea if it was because Arsenal didn't want to push the boat out a bit more."