The Reds boss eulogised his side's confidence in the UEFA Champions League during the build-up to the Group E clash at Artemio Franchi, but Jovetic gave the Spaniard a rude awakening.
Teenager Jovetic would perhaps not have featured if Fiorentina star Alberto Gilardino was not suspended, but he did not disappoint on his first start in the European Cup by producing an impressively energetic and skilful display.
Cesare Prandelli's Fiorentina deservedly took the lead in the 28th minute when Jovetic broke an unorganised Liverpool offside trap to collect a pass from the excellent Cristiano Zanetti and slot past Pepe Reina.
The 19-year-old then doubled his team's lead in the 37th minute as he deflected a Juan Vargas cross-shot to leave Benitez's shell-shocked side two goals behind at half-time.
Liverpool improved slightly in the second half, with Lucas Leiva heading over the crossbar shortly after the interval, but the damage had been done in a horribly out-of-sorts, continental performance.
Benitez's response to the loss of Javier Mascherano with a hamstring injury was to recall Brazilian defender Fabio Aurelio to his side.
Aurelio has had only a Carling Cup run-out against Leeds after a summer knee operation, and he was be used in a midfield role against the Italians, who are fourth in Serie A.
Quick and mobileOtherwise it was the same Liverpool side that beat Debrecen in the first group match.
Aurelio was used in a holding midfield role to allow Steven Gerrard to continue his advanced role supporting Fernando Torres.
But it barely worked, with Fiorentina quicker and more mobile. Martin Skrtel, at the back, had to be at his best to halt a run and shot from Jovetic, who from the resulting corner set up Marco Marchionni for an overhead effort that just cleared the bar.
Montenegro international Jovetic saw another effort flash wide after 22 minutes, Adrian Mutu having created the opening having beaten both Lucas and Aurelio in midfield.
There had been constant indecision in the Liverpool defence, and a failure to retain possession in midfield, and they were punished after 27 minutes.
Mutu was in a clear offside position on the edge of the box, but Zanetti's through ball was aimed at Jovetic - running from an on-side position - who was allowed to close in on Reina before guiding the ball past the Spaniard.
Reina needed to save well from Vargas soon after as Fiorentina sought to capitalise on their success.
The second was not long coming. After 37 minutes Marchionni crossed from the right and the ball found Vargas on the left. His low shot to the near post was deflected past Reina by Jovetic.
FlashLiverpool needed something quickly after the break, and Lucas saw a powerful header flash over the bar inside a minute of the re-start, before Sebastien Frey beat away a Dirk Kuyt drive.
Gerrard miskicked after good work from Kuyt, before Torres saw a low header deflected wide from Gerrard's cross.
Aurelio shot wide from a Torres set-up, but Fiorentina looked to have weathered the Liverpool storm at the beginning of the half.
Gerrard, who had been strangely quiet during the game, then saw a shot charged away by Massimo Gobbi from Lucas' chip.
Ryan Babel was sent on for Emiliano Insua after 71 minutes, with Aurelio switching to left-back. Fiorentina responded by sending on an extra defender, Martin Jorgensen for Vargas.
Skrtel was next to venture forward, and he got to the byline before crossing for Torres to fire over. Seconds earlier a frustrated Torres had been penalised as he set up Kuyt, who fired past Frey only to have the effort disallowed.
Next on was Andriy Voronin in place of Kuyt, as Liverpool searched for any way back into the match. Gerrard lifting a 20-yarder over did not help that quest.
FiorentinaTeam StatisticsLiverpool2Goals021st Half Goals04Shots on Target43Shots off Target63Blocked Shots34Corners109Fouls154Offsides30Yellow Cards00Red Cards073.5Passing Success8122Tackles2272.7Tackles Success63.639.3Possession60.755.7Territorial Advantage44.3