Team Sky will struggle to fill big gap at heart of team following Sean Yates' retirement A veteran of 20 grand tours as a rider and more as a directeur sportif with Discovery, Astana and Sky, Yates provided the main arsenal of tactical knowledge in what is still essentially a young team short on experience of winning the biggest races. In a squad well staffed with technical experts, conditioning gurus and nutritionists Yates spoke the riders" language and was highly rated by them, from Bradley Wiggins downwards. Their new mission is to win all three grand tours - the Giro d'Italia, the Tour de France and the Vuelta a España - in one season, a feat no team has previously achieved. Yates was earmarked for an important role in that task and will be fiendishly difficult to replace, especially as all potential candidates will find their past subjected to minute scrutiny under Sky's zero-tolerance policy, regardless of how far back any misdemeanours took place. Morale must have suffered a little recently following first the exposure of Michael Barry - who retired as a rider from Sky only last month - as a former drug cheat and the departure of coach Bobby Julich after he admitted his distant doping past. Couple that with the exit this weekend of Yates and the classics coach, Steven de Jong, and there has been a significant turnaround in personnel. Brailsford initiated this process while other teams tarried in response to the USADA report into Lance Armstrong, or ignored it altogether. Brailsford always predicted that the examination of his staff would be painful and would test him and his team to the full. He has also admitted past mistakes and insisted that they must not be replicated. However, he still believes that the almost utopian aim of fielding a demonstrably clean and trustworthy team is worth all the disruption to Sky. The weeks and months ahead probably represent one of the biggest challenges of his celebrated career.