Dimitrov meets Murray in Miami
He faces British world number three Andy Murray in the next round.
Earlier this year Dimitrov dropped just one set en route to his first ATP World Tour final in Brisbane (he lost to Murray).
Currently he is 32 in the world singles ranking – up from 48 at the start of the year.
Together with his partner Frederik Nielsen (Denmark) Dimitrov has also reached the second round of the doubles in Miami.