The 23-year-old Italian, fifth in the downhill standings, covered the 1,650 metres Gastrappet course in 1min 3.56sec, better than the German Regina Hausl by 0.08sec. France's Melanie Suchet was third fastest, 0.22sec off the pace.
The season's leading downhiller, Austria's Renate Gotschl, placed fifth on 1:03.91 as she looks to put some distance between herself and Germany's Hilde Gerg, who sits just 51 points behind with three races left in the season, including Saturday's event. Gerg was sixth in the training run.
"There is still a lot of time between now and Saturday so the main thing for me is to stay focused and relax," Gerg said. "I feel good on the skis so there are no worries from that standpoint, which is always the best way to enter a race."
The overall World Cup standings leader, Alexandra Meissnitzer of Austria, cruised through the run in 14th place as she prepared to put Wednesday's disappointing giant slalom race behind her, and keep Gerg from cutting too much into her 447 points lead.
"I made a mistake in the GS but that happens when you go all out. Sometimes you go just over the edge," Meissnitzer said. "But I feel fine and know I need to put some points on the board in the downhill, and that's my goal. I'll worry about the GS after that."
Organisers decided to use a two-leg sprint format for Saturday's downhill in the hope of avoiding the notorious fog here. By starting lower on the hill, officials hope to avoid delays that could be caused by adverse weather conditions higher up on the mountain.
At the Nordic World Championships at Ramsau, in Austria, Russia completed a decade unbeaten in women's cross-country 4x5km relay in major competitions when their quartet stormed to victory.
It was Russia's first success in an otherwise disappointing championships after dominating Nordic events in the 1990s. While Russia's win was expected, the day's other action featured a surprise as Finland edged out favourites Norway to snatch the Nordic combined. Finland beat Norway by 1min 14.7sec.