Sastre, 2008 winner who will not be competing in the Grande Boucle in 2011 for the first time in a decade with his team Geox missing out on an invitation, says that while the three-time winner should be considered "the number one favourite", there are "a lot of riders who have prepared well".
HTC-Highroad's Tony Martin is one such rider, according to Sastre who he says "surprised" him this year. Martin's season so far has been highlighted by overall victories at Paris-Nice, and the Volta ao Algarve, along with a second-placing to BMC's Cadel Evans at the Tour of Romandie.
"There are a lot of people this year who I'm sure will do really well and will not make it an easy task for Contador," said 36-year-old Sastre.
While the veteran explained he feels "pity" and "a certain amount of nostalgia" when it comes to his non-participation in this year's Tour de France, Sastre said that he realises "this is the situation this year."
He will instead ride the Tour of Austria, which starts on July 3.