of Roland Garros (l. to Ivan Ljubičić), and the semifinals of the 2006 Mercedes Cup (l. to José Acasuso). Following this semifinal appearance. he lost four matches in a row again a second-round loss in the Orange Warsaw Open (l. to Nikolay Davydenko) and a first-round loss at the US Open, BCR Open Romania, and the Kingfisher Airlines Tennis Open. He reached the third round of the AIG Japan Open Tennis Championships, losing to Jarkko Nieminen. He ended the year ranked number no. 69 in singles. In doubles, he made two semifinal appearance in the 2007 Brasil Open partnering compatriot Agustín Calleri, and in the 2007 Mercedes Cup partnering José Acasuso. 2007 2007 was Monaco's most successful year. Monaco started the year with a quarterfinal appearance at the 2007 Heineken Open, losing to compatriot Agustín Calleri. He also reached the quarterfinals of the 2007 Brasil Open losing to another compatriot Juan Ignacio Chela. Monaco entered his home tournament of 2007 Copa Telmex in Buenos Aires ranked at no. 66, and exited with his first ATP title dominating Alessio di Mauro in the final in straight sets. However, he exited in the first round of his next three tournaments in the Acapulco, Indian Wells, and a Challenger event. He reached the second round of the 2007 Miami Masters, losing to David Ferrer. He also reached the quarterfinals of the 2007 U.S. Men's Clay Court Championships, losing to American James Blake and at the 2007 Estoril Open (l. to Paul-Henri Mathieu). He qualified for the Hamburg Masters, but lost to top seed and eventual champion Roger Federer in the second round in three tight sets. Following his good performance against Federer, he went on to compete in the 2007 Hypo Group Tennis International in Pörtschach and won the title against Gaël Monfils. In the 2007 Mercedes Cup in Stuttgart he lost to Rafael Nadal in straight sets in the quarterfinals. He won his third title of the year in the 2007 Austrian Open in Kitzbühel after defeating the top seed Tommy Robredo in the quarterfinals and Potito Starace in the final. In the 2007 Cincinnati Masters, he defeated a player in the top 5 for the first time and the highest-ranked player he has defeated the world no. 2 at the time Rafael Nadal, when Nadal retired. Monaco lost to Sam Querrey in the third round. He also reached the quarterfinals of