The 30-year-old "Tommeke" from Mol, Limburg province, was Belgium's great cycling hope in the 2000s, named as the heir to Eddy Merckx. But after testing positive for cocaine use in 2008 and 2009, his career never quite recovered, and he has struggled to get back to winning.

This month, Boonen opened the season with appearances in two lucrative Arab circuits: he won one stage of the Tour of Qatar and completed the Tour of Oman. But even that was down on last year, when he won three Qatar stages and one in Oman.

Boonen is recovering from a number of setbacks. Last season was affected by crashes in the Tour of California and the Tour de Suisse. He missed the Tour de France and was forced to have knee surgery in July. Any hopes of recovering for the World Championships in September were dashed by a lengthy rehabilitation.

Since then, Boonen has been doing long, intense training sessions on the roads of Monaco, where he is now based. "My morale is good, and I'm very motivated," he told TV news last autumn.

But Boonen has not been the same since his drug bust. While it was not performance- enhancing like EPO (the drug of choice for the cyclists), it is still banned. And the fact that Boonen continued taking it a year after he was first caught, suggested a somewhat distracted temperament.

It was in 2005 that Boonen became the first cyclist to win the Tour of Flanders, Paris-Roubaix and the World Cycling Championship in the same season - and he also won the Belgian Sportsman of the Year award. In 2006, he held the yellow jersey on the Tour de France for four days, and the following year took home the coveted green jersey for sprinters, becoming the first Belgian rider since Eddy Planckaert in 1988 to do so.

This month, he questioned how three-time Tour de France winner Alberto Contador could escape suspension despite a positive doping test last year. It could be that Boonen is outspoken because he distinguishes between recreational drugs and doping. But given his history, he probably would do better to focus on his own form rather than point fingers.