Argentina\'s Juan Monaco celebrated his 28th birthday in style by surprising eighth-seeded American Mardy Fish 6-1, 6-3 in the quarter-finals of the WTA/ATP Miami Masters tournament on Thursday. Not many people gave underdog Monaco a chance against Fish, but the 21st seed has now won three straight against the American after dropping their first two matches back in 2005 and 2006. \"I can\'t believe it,\" Monaco said. \"I have a lot of emotions it is good to celebrate this way, playing unbelievable tennis on my birthday. \"Every shot I wanted to play I did. It was a perfect match for me. I returned well and then I served very, very good.\" In the semi-finals Monaco will face either world No. 1 Novak Djokovic or fifth seeded Spaniard David Ferrer, who were playing in the night session. Fish broke Monaco in the sixth game of the second set to make it 3-3 but Monaco responded by winning three straight, closing it out on the first of three match points with a backhand drop shot. This is Monaco\'s ninth appearance in Miami but the first time he has reached the semis. Monaco, of Buenos Aires, improved to 11-4 on the year and is chasing his second title of 2012 after capturing his fourth career crown in Vina del Mar in February. Monaco put on an impressive serving display by winning 71 percent of his first serve points as he needed just 82 minutes to oust Fish. The 30-year-old Fish, who lost in the second round at the Australian Open and in the third round at the Indian Wells Masters, fell to 7-5 in 2012. The hard-serving Fish finished with just one ace, one double fault and won 40 percent of his second-serve points.