Ernests Gulbis’ best Grand Slam result?

Question

What is the best result Ernests Gulbis, who just won his maiden ATP Tour singles title at Delray Beach, has achieved?

Answer 1

He seriously under-achieves. Has as much natural ability as anyone, including Nadal, but doesn't seem to have the hunger

I put it down to him being grotesquely wealthy. As a junior he would often travel to tournaments in his own private jet!

Had a good result beating Karlovic in two sets yesterday though

Answer 2

Gulbis was a quarter-finalist at Roland Garros in 2008, a run which included a second round defeat of then world No. 8 James Blake and which ended in the round of eight against then world No. 3 Novak Djokovic.  Since then, Gulbis has failed to progress beyond the second round of a major, most recently losing in the first round of the 2010 Australian Open to then world No. 33 Juan Monaco.