Alberto Contador (left) on the 2009 Tour de France podium with Lance Armstrong.

As Lance Armstrong and the “did he, didn't he” dope debate rears its ugly head again, the cynics doubting cycling's chances of freeing itself from its drug-tainted past may latch on to a fresh target: his former teammate Alberto Contador, who is fresh back from a drugs ban and battling for his biggest home race, the Tour of Spain.

After winning the 2009 Tour de France, Contador looked set to inherit his former Astana teammate's unofficial title as the dominator of the Tour de France. But a positive drugs test in 2010 saw the Spaniard stripped of that Tour victory – just as the US Anti- Doping Agency (Usada) want to strip Armstrong of his seven wins – and banned him for two years.

Both riders insist they are innocent, but there the parallels come to an abrupt end. Armstrong is ducking away from accusations by what Usada refer to as “numerous witnesses” of mass organised doping over eight years involving everything from the banned blood-booster EPO to blood transfusions. At the opposite end of the spectrum, Contador received the maximum ban after he tested positive for the banned steroid clenbuterol – but in a quantity 40 times below the minimum required by an anti-doping lab to be reported.

However, the lab decided to report the “positive” nonetheless, and a prolonged battle between Contador and cycling's governing body, the UCI, over his possible ban ensued – another difference, given the UCI have yet to come up with a definitive opinion about the outcome of the Armstrong case. Finally, in February this year, the Court of Arbitration for Sport, while admitting that the positive was more likely to have come from a contaminated food product than from blood doping, nonetheless banned Contador retroactively for 18 months, a ban which ended three weeks ago.

The Spaniard, 29, has received the warmest of welcomes inside his own country: at the Tour of Spain's team presentation he received by far the largest cheer, in stark contrast to the 2011 Tour de France, where he was booed. And his Team Saxo Bank bus is regularly besieged by huge numbers of fans and autograph hunters at each start.

Contador's performance in the Tour of Spain has so far been uneven – although he warned that would be the case. On the first climb of the race, to Arrate last Monday, he attacked no less than seven times.

On the second, to Ezcaray on Tuesday, he managed to break away briefly with the race leader, Joaquim Rodriguez. But on the third, the short, punchy ascent to Fuerte del Rapitan, Contador was dropped as Britain's Chris Froome and the Sky team upped the pace, losing nearly 20 seconds, and on the fourth summit finish he managed to gain 15 seconds on Froome by the Andorran climb of Collado de la Gallina but flailed suddenly at the finish and was unable to take the stage win, finishing third.

For now, Contador is nowhere near the rider who devastated the field on the climb to Verbier in the Tour de France in 2009, or who dropped the entire pack on the ascent to Mount Etna in the 2011 Tour of Italy. But even after losing that Tour title, with two Tour de France wins as well as victories in the Tours of Italy and Spain, in terms of Grand Tour results at least Contador remains head and shoulders above the rest of the current field. As such, a defeat in Spain – with Froome looking like the rider most likely to provide it – would raise yet more questions about Contador's status. The cliché about riders being less likely to perform well after returning from a doping ban will once again begin to circulate. Put in a nutshell, if he loses, the Spaniard may start to look like yesterday's man. – The Independent on Sunday