I have to say that Gulbis is one of the softest players on tour, but I don't know about being the worst. He does have talent, it just doesn't seem to be a real priority to him to put it to use on a consistent basis.
Even being the worst on the tour means you're one of the best in world.
Boris Becker London, Solinco Tour Bite @50 lbs.
Volkl PB9, Dunlop Hexy Fiber 16 @ 60 lbs.