Rast finished a close second to Shiffrin in last weekend’s previous World Cup slalom event in Semmering, but was not to be denied a second time, making sure the World Cup’s greatest skier could not add to her record tally of 106 wins in all disciplines.
“I think a lot of energy [was the key],” Rast added. “It was a big battle. My energy made the difference – the preparation was perfect.”
Shiffrin, 30, was just 0.1 seconds behind leader Rast after the first run, but set an imposing time in the second that opened a 1.69secs lead over the rest of the field.
But Rast went even faster to beat Shiffrin into second place by 0.14secs.
“I think about all those families and we raced for them this weekend,” the Swiss skier said on Saturday, saying her thoughts were with the relatives of those who lost their lives in her hometown.
“Sport brings emotion and I hope today I could bring some positive emotion for people.
“It’s really hard to know how it is when you are not home but for sure it is difficult, and I hope I could bring a little smile on some faces today.”
Shiffrin remained close to her best, despite the rare defeat, and will hope to get back to winning ways in the final two World Cup slalom events before the Winter Olympics begin in Milan and Cortina on 6 February.
Women’s World Cup slalom continues in Flachau, Austria, on 13 January, with the final event before the Winter Olympics taking place in Spindleruv Mlyn in the Czech Republic on 25 January.