The 28-year-old left the Gunners to join Barcelona, but failed to make an impact at Camp Nou.
The midfielder left the Spanish giants and joined former club Stuttgart on loan this summer.
Hleb said: “I regret leaving Arsenal. I was playing every week for one of the most exciting sides in Europe.
“I was being guided by one of the best coaches in the world and I owe Arsene Wenger a great deal. A footballer only truly exists when he takes to the field and makes a proper contribution to the team.
“But at Barcelona the season was spent with me almost entirely on the bench. I just couldn’t continue with them.
“I was part of the squad that was almost unstoppable but it was hard not to feel detached from all the happiness and celebration at the end of last season.
“I could have gone to Inter Milan on loan but I turned down Jose Mourinho to go back to my old club Stuttgart, where I was always very happy.”