He's earning peanuts at Pool (3m per year IIRC), thats the only reason I can think of as to why Deco is so obsessed with him. Nico at Bilbao earns +3 times more and was asking for a higher salary to leave last summer.
With his g+a today he reached 20 goals and 8 assists in 32 starts this season, not bad. Frankfurt play Spurs next month, so it should be interesting to see how he performs.