In 1997, playing against Ivanisevic (2nd seeded), in Long Island, beat him for first Top 10 victory en route to semifinal and in that match fired a 143 mph serve to become just third player (Philippoussis, Rusedski) to register a serve of at least 143.

He is the founder of ELITE TENNIS TEAM focusing on junior development and also is coaching pro players Leylah Fernandez, Arantxa Rus as many others before like, Qinwen Zheng, Mirjana Lučić-Baroni, Sabine Lisicki, Ajla Tomljanović, Varvara Lepchenko, Renata Zarazúa, Marco Cecchinato and Nicolas Almagro.

Previously, that same year, Tim Henman after being defeated by Alonso at "The Lipton" Key Biscayne (current Miami open) declared: "Julian will be the next number 1 in the World before Wimbledon"[2] After this promising start, however, his career is considered underwhelming; he only won one more title (Bologna, 1998) and retired in 2003 after half year playing only Challengers.

The pressure of the media and his mother-in-law made Alonso's ranking and self-confidence fall.

He used to play doubles in Davis Cup Spanish team with Joan Balcells during Manolo Santana captaincy, and several single matches.