His career started out anything but promising. Many first round defeats in small tournaments against lesser known opponents questioned his potential. In December 1996 he was able to book his first Challenger tournament victory in Santiago de Chile . In the final he defeated his compatriot Franco Squillari 7: 6, 6: 1 and finished the year in 226th place in the old ATP ranking . For the next two years he mainly played in Challenger tournaments to collect points. Due to his partial success, he leveled out in the top 100 of the rankings, which enabled him to participate in Grand Slam tournaments , where he was often eliminated in the first round. In April 2001 he won his first ATP tournament in Casablanca . In the final, he defeated the aspiring Tommy Robredo 7-5, 6-2. Another highlight of this season was the move into the round of 16 at the Grand Slam tournaments in Roland Garros and Wimbledon . He also reached three finals (in 's-Hertogenbosch on grass, in Stuttgart and Vienna on hard courts) and ended the year in 17th place in the ranking.
In the following years another six individual titles were added. In August 2005 he was banned from the players' union ATP for doping retroactively to June 11, 2005 for two years. One could convict him on the basis of the excessive consumption of water-laxatives, which are usually taken to prevent the detection of anabolic steroids . He was already the fourth tennis player in his country to be convicted of drug abuse. Previously, Guillermo Coria , Mariano Puerta and Juan Ignacio Chela had become conspicuous. The Argentine's suspension, which was originally due to end on June 11, 2007, was then shortened. Cañas, who reached the quarter-finals of the French Open in 2005, had to pay back $ 276,070 in prize money. In addition, the world ranking points that he had achieved during the period in question were deducted.
The comeback after the doping ban (2006-2007)
After his doping ban had expired , Cañas won the Challenger tournament in Belém in September 2006 and beat the number 94 in the world, Marcos Daniel from Brazil, 6-0 and 6-2. The year 2007 began for Cañas with another tournament victory at the Challenger in São Paulo against Diego Hartfield , who earned him $ 14,400 in prize money and 80 points for the ATP ranking. In addition, there was a renewed nomination for the Argentine Davis Cup team , which defeated the Austrian selection 4: 1 in Linz - Cañas won both of his singles. With the victories over Jurgen Melzer (7: 6 6 , 6: 2, 6: 4) and Alexander Peya (4: 6, 6: 1, 6: 4), he played a key role in the rise of the quarter-final, which beat Sweden 1: 4 was lost. In February he won an ATP tournament for the first time - in Costa do Sauipe in Brazil - with 7: 6, 4 and 6: 2 in the final over Juan Carlos Ferrero . This success brought him way up in the world rankings, so that from now on he could afford to play ATP tournaments and to do without Challenger tournaments.
On March 11, 2007 Cañas surprisingly defeated world number one Roger Federer 7: 5, 6: 2 at the Masters tournament in Indian Wells , but was eliminated in the following game against Carlos Moyá with 4: 6, 4: 6. On March 27, he managed another victory over Roger Federer, this time at the Masters tournament in Miami with 7: 6 (2), 2: 6 and 7: 6 (5). With further successes over Tommy Robredo (7: 6 and 6: 1) and Ivan Ljubičić (7: 5 and 6: 2) Cañas moved into the final of the tournament as a qualifier, which he beat Novak Đoković 3: 6, 2: 6 and lost 4: 6. At the end of April Cañas reached the final of Barcelona, in which he lost to Rafael Nadal 3-6 and 4-6. At the French Open Cañas reached the quarter-finals, where he was eliminated against Nikolai Dawydenko with 5: 7, 4: 6, 4: 6. At Wimbledon, he failed in round three to Lleyton Hewitt .
He celebrated his last success in November 2008 in doubles alongside Dmitri Tursunow .
After finishing his active career as a professional player, Cañas ran a tennis academy in Miami , Florida .