The 33-year-old Wiggins wasn't the only high-profile rider to withdraw, with team Garmin-Sharp's Ryder Hesjedal out of the race after succumbing to illness.
The race starts with a short team time trial in Venice on Saturday, with Stapleton's Team Columbia and the Garmin, Astana and Saxo Bank squads expected to feature.
Last weekend Garmin-Barracuda veteran Ryder Hesjedal secured the team's most significant victory ever: winning the Giro d'Italia, the three-week stage race second only to the Tour de France in prestige.