The absence of Basso leaves Cannondale mighty thin for the Giro and it's doubtful they can replace him with any firepower at this point. Presumably Cannondale will put in another helper for the sprints as Elia Viviani will now be left with the un-enviable task of being responsible for any results for the US/Italian team. A dream solution for the team would be to throw in the on-form Moreno Moser but he'd have to be on the registered shortlist for that to be an option.
In reality though this changes fairly little for the race as the chances of Basso repeating his win from 2010 were slim and even matching his 5th place of last year looked difficult. His support team didn't look as strong as last year either. Still, with his popularity in Italy he would have made Cannondale more visible in the race. Now they look to be a GC team without a captain unfortunately.
UPDATE: The spot on the team will be taken by Damiano Caruso who looked like the heir apparent to the GC-leader position on Cannondale in last years Giro. His form seems doubtful as he has raced sparingly this year and was last seen riding midpack in the Ardennes in support of Peter Sagan and Moreno Moser. If he can come good by the later half of the race he could be an interesting addition to the race. More interesting than a fading Basso in fact.