THOUSAND OAKS, Calif.

When Floyd Landis last week accused several top riders of doping, one thing was missing from the fallout: a flat-out, en masse denial of Landis’s allegations.

Some riders he accused, including the top Americans George Hincapie, Levi Leipheimer and David Zabriskie, declined to address the issue or were vague in their responses.

In a heart-tugging speech after the Tour of California ended here Sunday, Hincapie said that he had sacrificed himself for the sport and that he did not deserve to be accused of impropriety. A day earlier, Zabriskie had said he was disappointed to hear Landis’s claims.

Leipheimer said, “I really believe that cycling is much cleaner than the past.”

But the question remains: did those riders Landis has named — including the seven-time Tour de France winner Lance Armstrong — use performance-enhancing drugs back in the early to mid-2000s, when Landis said the doping occurred? And, if so, should it matter — especially if they might be clean now?