Pennant was snapped up for £2m from Notts County in 1999 when he was just 15.
And the ex-England under-21 ace claims he struggled to adapt after making the move.
He told The Times: "It was too soon for me.
"Looking back now, I wish I could have waited longer. Don't get me wrong. It was fantastic. Being at Arsenal, being around Thierry Henry, Patrick Vieira, all those great players and great coaches, was one of the best times of my career.
"That was almost five years.
"Frustration crept in and I didn't handle the pressure well. I didn't have the discipline. That caused havoc for me."