The BATE Borisov midfielder joined the Spanish giants from Arsenal in 2008 but failed to play regularly in his four years at Camp Nou, going on loan to Stuttgart, Birmingham City and Wolfsburg.
"I learned more from [Arsenal manager Arsene] Wenger than Guardiola, but Pep is a good coach," the 31-year-old told Esports en Xarxa.
"Guardiola is not the best coach in the world because he coached the best team in the world, with the best players, and that's why he won. It's hard not to win with a team like that and [Tito] Vilanova will have the greatest success.
"The best coaches in the world are [Jose] Mourinho, [Sir Alex] Ferguson and Wenger."
Hleb returned to BATE in July 2012.