After it was demonstrated that the intake of clenbuterol, Puerta was banned in 2003 for nine months. The significant weight gain during this period earned him the nickname " el gordo " ( the thickness).
In June 2005 he reached his first Grand Slam final at the French Open. However, it was announced then that Puerta was also tested positive for Etilefrin there. Mariano Puerta was closed on 21 December 2005 for eight years, but appealed against the judgment set aside. On 12 July 2006, a reduction of the barrier to two years was announced.
On 5 June 2007 he was at the Challenger tournament in Sassuolo his comeback, for which he received a wild card. He defeated after his doping break Joseph Sirianni of Australia 6-4, 6-3.