This was arguably the smartest move he could make. He's coming off a disappointing season so he's going to a mid-table team in one of Europe's strongest leagues to seize his new opportunity. For god's sake, he's 22! He's got YEARS ahead of him. Two good hears at HSV and he'll be moving to a major club WELL before he reaches the age when most football players reach their peak.
At a big club he would never have succeeded at this point in time. This way, he's going strong. Remember: he has had so much hardship to deal with (injuries, failing coach, the burden of carrying a squad at a young age) that it's a very good move for him to check out a 'quiet' squad first so he can develop in peace for a change.