Alejandro Valverde said the lay-off from a doping ban has hurt Alberto Contador's chances of winning Vuelta a España.
Contador returned to competition earlier this month after being banned since February for testing positive for clenbuterol en route to winning the 2010 Tour de France, a title of which he was subsequently stripped.
The 2008 Vuelta champion trails overall leader Joaquin Rodriguez by one minute in this year's edition to sit in third place. Contador is seven seconds behind Briton Chris Froome and the same time in front of the fourth-placed Valverde.
"He's been laid off for a while, so he is still trying to find his rhythm," Valverde said yesterday, the first rest day of the three-week race. "He's a little nervous, attacking when he shouldn't be."
Contador, like Froome, will be looking to get through today's 10th stage with his gap to Rodriguez unchanged as tomorrow's time trial gives a chance to gain ground.
Valverde, the 2009 champion, believes Froome is favourite in the time trial, even if the Briton is tired after a long season in which he was Tour and Olympics runner-up.
"Froome is the most favoured for the time trial, but he still looked a little drained," Valverde said.