Hleb was top class for the first half of the 2007-2008, probably the best player on form in that side along with Adebayor. He was pretty average apart from those 20 games though; played slightly better in Europe through his tenure because it suited his playing style more.
But then like so many others in that era, he fucked off as soon as he showed good form. Pretty mind-boggling that Adebayor, RVP, Fabregas (he had two top class seasons to be fair), Nasri, Hleb, and even Flamini all left after playing well for one season.