Tour de France veteran Stuart O\'Grady has called on Leopard teammate Andy Schleck to deliver the knock-out blow that will put paid to Alberto Contador\'s reign. Schleck has finished runner-up to the Spaniard the past two years, but comes into the race this year determined as ever to claim stage racing\'s most coveted prize. While the Luxemburger is sure to benefit from the fact that Contador recently spent precious energy during a triumphant Giro d\'Italia campaign, O\'Grady believes Schleck would do himself a favour if he turned nasty. \"Of course no one wants to have enemies but at the end of the day we\'re out there to win, they both want to win as much as each other and they both want to do it fairly -- which is how it should be,\" said O\'Grady. \"But when the gloves come off, you\'ve got to go for the knock-out blow. \"I think the guys have got to stop being so friendly. It\'s a boxing ring out there for three weeks.\" One of the show-stopping moments in 2010 was Contador\'s decision to attack Schleck when the Luxemburger, then wearing the yellow jersey, was delayed when his chain came off late on a crucial mountain stage. Crucially, Contador went on to take the race lead as a livid Schleck hit out at the Spaniard, who was also booed by some fans on the podium. Previously, the pair had highlighted the friendly nature to their rivalry. But a Contador apology failed to stop a wedge being driven between the pair. Schleck has said repeatedly he has not forgotten. And O\'Grady believes Schleck won\'t be so naive this year. \"What happened last year, with chain-gate, as devastating as it is he is never going to forget that,\" added the Australian. \"He\'s going to take something from it and it will help him grow as a person, as an athlete and hopefully it will never happen again. \"Andy is now more confident. And we do have a super-strong team here. If ever we can do it, this is a great opportunity.\" The crucial third week, held in the Alps this year, will be decisive this year. And having won the race\'s white jersey for the best placed rider aged 25 and under the past three years, that is no longer possible for the 26-year-old Schleck. \"Andy\'s always had the white jersey as a back up plan, but that\'s gone and I\'m glad that\'s gone,\" added the Australian, who was part of the CSC team with Schleck who helped former teammate Carlos Sastre win the Tour de France in 2008. \"It\'s nice to have... but he\'s a bigger rider than that. Now it\'s time for him to concentrate 100 percent on winning the Tour de France.\" Despite the presence of other potential challengers -- such as Australian Cadel Evans, Britain\'s Bradley Wiggins, Dutchman Robert Gesink and Jurgen van den Broeck of Belgium -- the Contador v Schleck duel will be compelling. Brushing aside the significance of a mitigated performance at the Tour of Switzerland two weeks ago, Schleck said he is ready to go. \"I\'m going into the Tour calmer than last year, because I know I\'m ready and once we get into the mountains I know I\'m going to be up there.\"