Blatt has been referred to as a "Euro legend" in several headlines. He was the coach of Tel Aviv Maccabi, the reigning Euro League champs.
As previously discussed with the Micic post, I don't watch a ton of Euro ball but Blatt has a long, storied track record of success. The guy does not lose, ever (at least in international basketball).
A glance at his coaching record (available here) shows you that the guy wins. He's had one losing season in his career (which started in 1993-1994) and he went 7-8 during that year. He went .500 twice. Every other season the guy has had a winning record.
His last four seasons have been particularly impressive. In 2010-2011 his team went 26-1. His winning percentage during the last four years never dipped below 78.6 percent.