The 21-year-old UAE rider Juan Ayuso won the opening time trial in a manner that put him in the mix for the overall title at the Tirreno-Adriatico on Monday.
The Spaniard edged out double time-trial world champion Filippo Ganna by clocking 11min 24sec, and was also 24 seconds ahead of the race favourite, Denmark's Jonas Vingegaard.
Only 10km long around a seafront lido, the course was dotted with several nasty 90-degree turns, where urban time trials are generally won and lost, and subject to a headwind before the course turned back to the lido.
Ayuso's feat came a day after his teammate Tadej Pogacar demolished the opposition at the Strade Bianche one-day race.
Ayuso described the win as morale-building, and confidently put himself in contention for the title despite the five former Grand Tour winners present at the race.
"It's great, I wasn't sure I'd beat Ganna but he was the man to beat, so it's very emotional, a great victory and a morale boost for the overall race," said Ayuso.
"I wasn't sure if I could win this time trial, but I did know I would do better than the GC guys."
When asked if he could beat two-time defending Tour de France champion Vingegaard he barely skipped a beat.
"It'll be hard to beat him but we're going to give our best," he said, accompanied by Team UAE chief Mauro Gianetti, who also discovered and brought through Pogacar.
Three former Giro winners Ecuador's Richard Carapaz, Australia's Jai Hindley and Britain's Tao Geoghegan Hart, and former Vuelta champion Simon Yates are also at the race.
Tuesday's stage two from Camaiore to Follonica is set up for a bunch sprint but with two mountain and two hilly stages upcoming, a punishing stage six looks to be where the "Race of the Two Seas" will be won.