The BATE midfielder helped the club shock Bayern Munich by beating them in the Champions League in the most recent round of European fixtures.
However, Hleb seems a lot more doubtful of pulling off a surprise victory against Vicente del Bosque’s men.
“Spain are the best team in the world. Who can beat them?” the 31-year-old said to reporters on Thursday.
“They are pure talent. When they play they look like they enjoy their football.
“The Spanish have the ball most of the time and we will have to defend ourselves. A draw would be great. Victory? Unrealistic, [it would take] a miracle.”
Belarus lost their first two matches 1-0 and 3-1 against Georgia and France respectively and Hleb insists his country are going through a transitional period.
The former Barcelona midfielder said: “We are under reconstruction. Veterans are no longer around, but young people still need time to mature.
“Belarusian Football is evolving, but it is still difficult to compete with other European teams.
“[But] if we go out without fear, as in the second-half against France, we can play well.”
Hleb admitted he has fond memories of his time at Camp Nou despite being limited to sporadic appearances under former coach Pep Guardiola.
“I think I could have played more,” he mused. “But Guardiola relied on other players. I tried to find a common language, but now I blame myself more.
“I was angry with him. I behaved like a child. Now, it makes me angry, but that's football.”