Sevilla beats Fiorentina 3-0 in Europa League semifinal
Fiorentina had the better share of chances in the first half, but it was Vidal who struck first from long range in the 17th minute at Sanchez Pizjuan Stadium.
Vidal deflected on a ball in the 75th for substitute
"Fiorentina got here because they deserved to, but we stuck to our playing style in our stadium and we have earned a great result," Vidal said. "If I were to say the tie is still 50/50, I would be lying. But we can't relax because they can get a win by the same score we had today."
The return leg in Florence is next week.
In the other semifinal, Ukrainian club Dnipro earned a 1-1 draw at Napoli.
Joaquin Sanchez, jeered by the Sevilla faithful for his past at crosstown rival Real Betis, was in inspired form from the start on the left side of Fiorentina's attack, and his pass for Mario Gomez produced the game's first scoring chance in the fifth.
Sevilla countered through left back Benoit Tremoulinas, and its opening goal came from a quick buildup on his side. The ball flowed through Jose Antonio Reyes and Victor "Vitolo" Machin before Carlos Bacca laid off for Vidal to rifle a long strike into the corner of the net.
"At home we had to impose our superiority on the flanks, and our effort was tremendous," Sevilla coach Unai Emery said.
Joaquin led the visitors' response two minutes later as he dribbled down the endline before setting up Matias Fernandez, who stunned teammates and opponents alike when he misfired from inside the six-yard box.
The match continued at a frenetic pace, but the Italian side had the best opportunities as both Fernandez and Mohamed Salah drew saves from close by goalkeeper Sergio Rico.
Sevilla doubled its lead when Vidal again arrived unmarked in a second wave.
Vidal, who Emery has converted from forward to speedy defender, received Vitolo's pass deep in Fiorentina's box, where he slotted the shot in after goalie Neto dove from his line expecting a cross.
Gameiro scored seconds after coming on when Tremoulinas broke down the left to cross for Vidal, who sent the ball on for the forward to put home.
The second half featured a scary head-to-head collision when Sevilla's Stephane Mbia slammed his forehead into the back of Milan Badelj's head. Both players were substituted with Badelj bleeding and Mbia holding his neck.