Wojciech Szczesny says he 'learned more in four months' in Italy than in 10 years in England'.
The 29-year-old Polish international, who is currently thriving in Serie A with Juventus, joined the Italian giants after falling out of favour at Arsenal.
Having seen his place in the side taken, Szczesny initially joined Roma on loan in 2015.
Such was his improved form under Luciano Spalletti, that he was snapped up by Juve in 2017.
Speaking to Il Tempo, the shot-stopper explained the reason for leaving Arsenal in the first place.
He said: "If I (was to) stay at Roma, it'll be the opportunity to grow and improve even more. If I return to Arsenal, I'll make use of my experience.
"I learned more in four months under (Luciano) Spalletti than in 10 years in England. He puts a lot of importance on playing the ball to feet. One day we trained for over 45 minutes just on goal kicks."
Szczesny added: "I consider this season very positive, I had to change mentality quickly, it was a very important opportunity for me.
"It was a waste of time sitting on the bench in London."
Szczesny recently signed a contract extension to keep him at Juve until 2024.