Italy's Adriano Malori won the amended opening stage of the Tirreno-Adriatico, edging out favourite Fabian Cancellara in an individual time trial.
The 3.4-mile route in Lido di Camaiore, Italy was reduced by 10 miles because of debris on the road after high winds.
Malori won in six minutes, four seconds to beat Cancellara by one second.
Steven Cummings was the best Briton as he finished eighth, six seconds behind the winner and Mark Cavendish was 12 seconds off the leader's pace.
This year's race was set to be the first time that four riders with 10 Grand Tour wins between them have competed together in a World Tour stage race.
But 2013 Tour de France champion Chris Froome withdrew on Monday because of a chest infection.
Defending Tirreno champion Alberto Contador, reigning Tour de France champion Vincenzo Nibali and last year's runner-up Nairo Quintana are in the race.
Contador finished 19 seconds behind Malori after a poor start, leaving him eight seconds behind Nibali and nine behind Rigoberto Uran Uran.
Thursday's second stage is a mainly flat, 153km (95-mile) route from Camaiore to Cascina.
The 50th edition of the race across central Italy ends on 17 March with another individual time trial.
Tirreno-Adriatico Stage One result
1. Adriano Malori (Ita/Movistar) 6mins 04secs
2. Fabian Cancellara (Swi/Trek) +2secs
3. Greg Van Avermaet (Bel/BMC)
4. Maciej Bodnar (Pol/Tinkoff - Saxo)
4. Matthias Braendle (Aut/IAM)
6. Daniel Oss (Ita/BMC) +4secs
7. Ramunas Navardauskas (Ltu/Cannondale) +5secs"
8. Steven Cummings (GB/MTN) +6secs
9. Peter Sagan (Svk/Tinkoff - Saxo)
10. Johan Le Bon (Fra/FDJ) +8secs
21. Vincenzo Nibali (Ita/Astana) +11secs
30. Mark Cavendish (GB/Etixx - Quick-Step) +12secs