Can clean cyclists be dominant?

Vincenzo Nibali of the Astana team came tantalizingly close this season to doing something that hasn't been done in cycling in a long time: win two grand tours in the same year.

After barnstorming to victory in the Giro d'Italia, Nibali ran into a brick wall in the form of 42-year-old Chris Horner at the Vuelta a España, where Horner became the oldest grand tour winner in history and relegated Nibali to runner-up status.

Winning two grand tours in one season is among cycling's most elusive accomplishments, a pinnacle that's been reached only 12 times in the sport's history. The last to do it was Alberto Contador, who won the Giro and Vuelta a España in 2008, the year organizers prevented his Astana team from starting the Tour.

Though Nibali fell short of the double this year, he is rewriting the history books in another, more intriguing way. The 29-year-old Italian has already done something that is unique in the "new cycling" era, becoming the first to win more than one grand tour since the focus on doping enforcement in recent years.

It's a slippery slope trying to define when and where cycling's newer, cleaner reality began. Elements of the biological passport, the no-needle policy, the whereabouts program and increased out-of-competition testing date back to 2008.

In 2007, there were signs that the peloton was lurching toward a cleaner, more credible place, but it took several seasons and many more doping scandals to transform things. And the paradigm shift is far from over.

You can draw a seemingly clean line from 2010, straight from the middle of Contador's positive test for clenbuterol in that year's Tour. Contador's clenbuterol case, which remains highly controversial for a variety of reasons, is one place where cycling could try to designate a "before and after."

"Before" includes a sport mired in controversy and doping scandals, forming peloton who would win at any cost. "After" is represented by today's new-look cycling, which is built on more credible performances.

While it's unfair to claim that all riders before 2010 didn't race or win clean, and equally naive to suggest that all of today's riders are racing on bread and water, 2010 does serve as an interesting watershed for the sport.

Since Contador's clenbuterol case, the performances are undeniably more believable. Some of today's veteran stars still have issues in their collective past, but the performances over the past three seasons have been relatively scandal-free.

There are exceptions, of course, including Ezequiel Mosquera's doping positive while running second behind Nibali in the 2010 Vuelta, and Fränk Schleck's doping case in the 2012 Tour, a year after sharing the Tour podium with his brother, Andy.

If we dare to believe what we see and what the doping controls are telling us, however, it's not a stretch to say that cycling today is the cleanest it's been in decades, and perhaps even in the entire history of the sport.

For the most part, 2010 can serve as a place to reset the odometer to zero.

In the overall context of a cleaner peloton, there's an interesting plot line that will play out over the next several seasons: Will the "new cycling" see the emergence of another singular Tour rider?

Over the past half-decade, the peloton has seen a series of charismatic, dominant riders who were the reference of their generation. From Jacques Anquetil to Eddy Merckx and Bernard Hinault, continuing with Miguel Indurain and the scandal-marred Lance Armstrong, the sport has been dominated by a series of larger-than-life captains who conquered their respective eras.

The sport has been in transition at many levels since 2010, though. One of the most interesting facets is that there has yet to emerge a dominant rider characteristic of those who ruled the sport since the 1960s.

The demands of modern, cleaner cycling require months and months of discipline, sacrifice and hard work, something that's harder to maintain and reproduce without the benefit of pharmaceutical assistance.

Riders such as Armstrong were fueled by EPO, blood transfusions, testosterone patches and perhaps a few well-placed bribes along the way, allowing him to rip through seven consecutive Tours like butter.

Flash forward to 2010, and things are suddenly quite different. The demands of today's clean(er) racing seem to completely wipe out riders after winning the Tour. As such, Nibali is the only one who's managed to win more than one grand tour since 2010.

What's certain is that the sport is enjoying a string of one-off grand tour winners not seen since the mid-1990s.

Part of the power void stems from a generational change at the top of the peloton. Cadel Evans won the Tour in 2011 at 34, while Bradley Wiggins won last year's Tour at 32. Both flamed out in their respective Tour defenses and likely will never again challenge for a yellow jersey.

A few older riders, such as Alejandro Valverde and Joaquim Rodríguez, are still knocking at the door. Horner broke records at the Vuelta, but might never race another grand tour again if he cannot find a contract. Managing one more grand tour would be a huge success for any of them.

Crashes and health issues can cripple anyone's aspirations at any moment -- that much hasn't changed. Andy Schleck, a four-time grand tour runner-up, is still struggling with injury and form since his 2012 crash.

It took Nibali more than two years before he could win the Giro following his 2010 Vuelta victory. And success at the Giro and Vuelta is always considered a step below the Tour, both in terms of physical and psychological demands.

Juanjo Cobo, the rider who beat Chris Froome at the 2011 Vuelta, is a rider with a long history of occasional brilliance undermined by lapses in mental fortitude. He was so out of shape this year that Movistar didn't even bring him to the Vuelta, and he doesn't have a contract for 2014.

Contador, on the other hand, is a unique case. By far the most prolific and successful grand tour rider of the post-Armstrong era, the Spaniard seemed destined to challenge Eddy Merckx's record of 11 grand tour victories.

Though Contador had two grand tours stripped away -- the 2010 Tour and the 2011 Giro -- he still has five and ranks as the most successful active rider. His 2012 Vuelta victory was as electrifying as any in recent cycling history, but the "Pistolero" was firing blanks this summer and seemed a shadow of his former explosive self during this year's Tour.

And it remains to be seen whether Contador, who will turn 32 on Dec. 6, can once again become the lethal grand tour rider he once was.

Stepping boldly into this vacuum is Froome, who could well emerge as the first multiple tour winner in the post-EPO era.

He's already shown consistency and determination over the past few seasons, riding to second at the 2011 Vuelta and again at the 2012 Tour, two races he very well could have won if he had not been held back to help Wiggins.

With Team Sky well ahead of its rivals on many levels, Froome's ascent seems assured. By all accounts, the 28-year-old has the maturity and character to match the strength of his legs. There's every indication that the Sky captain will not fly off the rails, but nothing in cycling can ever be taken for granted.

He'll face a formidable challenger in Nibali, far and away Froome's most dangerous rival. There is also Nairo Quintana, the sensation of the 2013 Tour, but the young Colombian needs to confirm that his superb performance this summer was no fluke.

Quintana's climbing pedigree is unquestioned, but his handicap against the clock might prevent him from ever winning a Tour, especially if Froome and Nibali -- two superior time-trial riders -- are at the top of their games.

Cycling's always had big champions, yet as the sport readjusts to cleaner racing, it will be interesting to see if history repeats itself in that way.

Are we seeing the beginning of the Froome era? Or are the demands of winning the Tour cleanly so high that the human body can meet its demands only occasionally?

Will "new cycling" see every grand tour so wildly unpredictable and wide open that any one of a dozen or so candidates could emerge the victor, only to fade away, and see someone else step forward?

Those questions assure that the 2014 Tour will be interesting in more ways than one.