5. Mariano Delfino
Delfino was one of the most unlikely people to end a career of a former No. 1, such as Marcelo Rios. How could an Argentinian Challenger player, who peaked at No. 154 be the last person to face Rios? The truth is that Rios’ body was what truly defeated him. The Chilean missed the second half of the 2003 season due to back problems, and tried his luck on the Challenger tour in 2004. He lost in the 2nd round of his first tournament after defeating Florent Serra against Delfino. Rios won the first set 7-5, dropped the second 3-6 and then retired, not only from the match, but from tennis. This was definitely Delfino’s most significant moment on tour, dwarfing his Challenger titles. Delfino retired 4 years later, after losing 0-6 0-6 to a fellow Argentinian Leandro Migani in the opening round of a Futures in Argentina.
