Cycling: Contador in shadow of Armstrong

Since returning from his drug ban the Spaniard is battling hard to keep up in the Tour of Spain

Reign in Spain: Alejandro Valverde wins yesterday's Tour of Spain stage from Joaquim Rodriguez (right) and Alberto Contador (AFP)

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 team-mate 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 team-mate'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 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.

Meanwhile, Froome, second last year, is racing the Tour of Spain for the first time as a leader without Britain's Tour de France winner and team-mate Bradley Wiggins at his side, and has yet to prove he can handle that pressure.

"It's a very different ball-game if you are racing in somebody's shadow or racing as the top leader alone, like Froome has to do now without Wiggins," said Rodriguez's team manager, Dimitri Konychev. "When someone can race alone, that's a real sign of a champion."

Rodriguez, six years Froome's senior, is also raising the bar. At 33, his defeat in the 2012 Tour of Italy could hardly have been narrower, just 16 seconds behind Canada's Ryder Hesjedal – and it was the Katusha rider's best Grand Tour result to date.

In the Tour of Spain, as Konychev puts it, "it's win or nothing this time", but the race's sole time-trial, next Wednesday, is yet to come, and that is his weak point.

The real moment of truth for all three contenders, though, is the trio of mountain stages next weekend. In increasing order of difficulty, Saturday's ascent to Ancares is steep enough to be perfect for Rodriguez, while Sunday's longer ascent to the Lakes of Covadonga is more like the Angliru climb, where Contador has won in the past.

Next Monday's 19.4km ascent to Cuitu Negru, though, is more like the Alpine and Pyrenean passes where Sky and Froome dominated this summer. But there, however, they did not have Contador or Rodriguez as opponents.

Yesterday's stage

Alejandro Valverde overtook the overall leader, Joaquim Rodriguez, and Alberto Contador on the final climb to win the eighth stage of the Tour of Spain yesterday.

The Spanish rider surged past his compatriots after the last turn to cap a gruelling climb over the closing kilometres to finish in a winning time of 4hr 6min 39sec. Contador struggled in the Andorran Pyrenees before giving way, though he finished in the same time.

Britain's hope Chris Froome could not keep up with the Spanish trio and finished 15sec behind in fourth place, falling further behind in the overall standings.

Rodriguez's overall time of 29:59.35 allowed the Katusha rider to stretch his overall lead over the second-placed Froome by 23sec to 33sec.

Contador dropped 4sec on the stage to sit 40sec back overall, while Valverde gained 4sec to trail Rodriguez by 50sec.