Tennis world number one, Novak Djokovic , will face Alexandr Dolgopolov, a 7-5 6-4 winner over Brazilian Thomaz Bellucci, in the fourth round.
Djokovic, who is seeking a fifth win at Miami, wrapped up a one-sided first set in 26 minutes but faced a sterner test in the second.
Darcis broke to go ahead 5-4 but after the Serb levelled up the set, he broke back and held on to secure the match.
“I managed to come back in the right moment,” Djokovic said.
“I kind of elevated the intensity and started playing a little bit more with depth on the ball.
“He’s got a lot of variety, especially from his backhand side.
“So I was handling it really good for first 30 minutes, then started to make some unforced errors and started to play a little bit more neutral, a little bit slower, and he got into the match.
“I complicated my own life in the second set but in the end of the day, it’s a win.”