Alberto di Bernardo came off the bench to kick a last gasp penalty and seal a stunning comeback 22-20 win for Treviso over the Scarlets.
It took the visitors a while to get going in northern Italy as fly-half Rhys Priestland missed with an early penalty attempt and the only score that either side could muster in the opening 25 minutes was a Priestland drop-goal.
The Welshman did eventually show why they are flying high at the top of the RaboDirect PRO12 table though and, despite resting the likes of George North and Scott Williams, they scored the game's first try through winger Andy Fenby.
And, although Treviso did hit back swiftly with a try from hooker Leonardo Ghiraldini, the Welshmen reasserted a measure of control late on in the first half as Fenby showed excellent footwork and pace to grab his second try of the night and his fifth of the campaign so far.
Priestland added the conversion to make it 17-5 at half-time and, when he kicked another three points early in the second half, it looked as if the men from Llanelli were moving inexorably towards their fourth victory of the season.
The Italians had other ideas though and Fabio Semenzato, who only came on for Kris Burton at half-time, got them back into the match with a smart try 10 minutes after coming off the bench.
All of a sudden Treviso were on a roll and, when Robert Barbieri continued his impressive start to the season with his fourth try of the campaign already, the deficit was reduced to just a solitary point at 20-19 and there was still quarter of an hour left to play.
The Scarlets kept them at bay bravely, despite having number eight Rob McCusker sinbinned in the final ten minutes, but their resistance finally cracked in the dying seconds as they conceded a pivotal penalty.
Substitute di Bernardo stepped up to kick the three points and give the home side a remarkable comeback victory against the shell-shocked Scarlets, who may rue the decision to leave some of their big guns back home.
Tries: Barbieri, Ghiraldini, Semenzato
Cons: di Bernardo 2
Pens: di Bernardo
Tries: Fenby 2
Cons: Priestland 2
Treviso: 15 Luke McLean, 14 Tommaso Benvenuti, 13 Alberto Sgarbi, 12 Luca Morisi, 11 Tommaso Iannone, 10 Kristopher Burton, 9 Tobias Botes, 8 Robert Barbieri, 7 Alessandro Zanni, 6 Simone Favaro, 5 Valerio Bernab˛, 4 Antonio Pavanello (capt), 3 Lorenzo Cittadini, 2 Leonardo Ghiraldini, 1 Michele Rizzo.
Replacements: 16 Franco Sbaraglini, 17 Ignacio Fernandez-Rouyet, 18 Pedro Di Santo, 19 Francesco Minto, 20 Dean Budd, 21 Paul Derbyshire, 22 Fabio Semenzato, 23 Alberto Di Bernardo.
Scarlets: 15 Jordan Williams, 14 Liam Williams, 13 Gareth Maule, 12 Jon Davies, 11 Andy Fenby, 10 Rhys Priestland, 9 Gareth Davies, 8 Rob McCusker (capt), 7 Johnathan Edwards, 6 Josh Turnbull, 5 George Earle, 4 Sione Timani, 3 Deacon Manu, 2 Matthew Rees, 1 Phil John.
Replacements: 16 Ken Owens, 17 Peter Edwards, 18 Samson Lee, 19 Aaron Shingler, 20 Kieran Murphy, 21 Tavis Knoyle, 22 Adam Warren, 23 Kristian Phillips.
Referee: Andrew McMenemy (Scotland)