Millar tumbled to eighth overall after the team time trial
David Millar's hopes of becoming the first Briton to lead all three grand tours were dashed in stage four of the Giro d'Italia, a team time trial.
The Scot, who wore the Tour de France yellow jersey in 2000 and the Vuelta a Espana's gold jersey in 2001, started the day one second off the lead.
But he ended 45 seconds back after his Garmin-Transitions team came eighth.
Vincenzo Nibali took the pink jersey after leading his Liquigas team to victory while Team Sky finished second.
Chris Sutton was an early casualty for the Sky outfit after suffering a puncture within minutes of the start.
But the remaining riders built a four-second advantage at the intermediate checkpoint in wet conditions.
In the closing stages, Mathew Hayman, Chris Froome and Michael Barry fell back after big shifts at the front.
But Morris Possoni, Greg Henderson, Steve Cummings, Dario Cioni and Bradley Wiggins were still together as they crossed the finish line.
They led the standings briefly before Italian Nibali's squad - finished the 32.5 km time-trial between Savigliano and Cuneo in 36 minutes 37 seconds, 13 seconds quicker.
Team HTC-Columbia were third, a further eight seconds adrift.
The result handed Nibali a 13-second lead over team-mate Ivan Basso in the general classification, while Alexandre Vinokourov, who began the day in the maglia rosa following three stages in Holland, dropped to sixth overall.
Nibali, who finished seventh in last year's Tour de France, was only called up for the race at the last minute after Franco Pellizotti was accused of doping.
But he now leads team-leader Basso, who served a two-year ban for doping between 2007 and 2009, going into Thursday's 162km fifth stage between Novara and Novi Ligure.
Giro d'Italia provisional standings:
1. Vincenzo Nibali (Italy / Liquigas) 10:44:00
2. Ivan Basso (Italy / Liquigas) +13
3. Valerio Agnoli (Italy / Liquigas) +20
4. Andre Greipel (Germany / HTC - Columbia) +26
5. Matthew Goss (Australia / HTC - Columbia)
6. Alexandre Vinokourov (Kazakhstan / Astana) +33
7. Vladimir Karpets (Russia / Katusha) +39
8. David Millar (Britain / Garmin) +45
27. Cadel Evans (Australia / BMC Racing) +1:59
50. Bradley Wiggins (Britain / Team Sky) +4:36
62. Steven Cummings (Britain / Team Sky) +8:51
75. Charley Wegelius (Britain / Omega Pharma-Lotto) +9:35
173. Chris Froome (Britain / Team Sky) +15:10