His salary isn't as bad as what people make it out to be. 20 Million isn't much now a days and in a few years will be what 12-15 million is now. Hardly a zero-asset. If Jeff Samardzija is going to get $75-80 million after a subpar season with the QO attached then Tulo is getting a ton more than 5/100 even though he had a bad year.
And besides, this would be a terrible time to trade him as there aren't any better options to replace him with.
http://www.foxsports.com/mlb/just-a-bit-outside/story/free-agency-hot-stove-rumors-contracts-busts-david-price-zack-greinke-davis-weaver-werth-111115