Ospreys missed the chance to move back into second in the Guinness PRO12 table after Treviso upset the form book with a win at the Stadio Comunale di Monigo.
Neither side showed their full capabilities in a low-scoring game but a try from Alberto Sgarbi and penalties from Tito Tebaldi and Ian McKinley were enough to secure the win.
Treviso showed their intent from the start and launched an attack that got within five metres of the Ospreys line, but a knock on left the home crowd unfulfilled and Ospreys could clear.
The home side kept coming though and had a chance to trouble the scorers from the kicking tee, but the penalty from Tebaldi drifted wide after eight minutes.
It remained all Treviso, though, until Ospery’s Dan Baker took advantage of quick ball from the back of a five metre scrum and ended up breaking to the half way line.
The home side did not have long to wait for their first breakthrough, though, as Sgarbi finally made the pressure tell and crossed in the 18th minute for the opening score – converted by Tebaldi.
Errors and knock-ons from both sides kept the game a scrappy affair until a break from Keelan Giles lit up the play five minutes later – Treviso forced him into touch before he could do any real damage, though, as Ospreys struggled to make an impact on the game.
The try did come though and it was that man Giles again, as the lightning-quick winger latched onto onto quick ball fed from Sam Davies to Dan Evans and went over in the right corner for an easy score with the clock in the red – the fly-half missed the conversion though to send Ospreys in trailing by two.
Neither side could settle into the game as more errors characterised the opening to the second period, but when Ospreys were penalised for wheeling the scrum Tebaldi could kick to the corner with 50 minutes gone.
Treviso could not build on the platform, however, instead turning the ball over and allowing Ospreys to clear their lines.
But they did extend their lead just before the hour, with Tebaldi kicking a routine penalty after Ospreys were again penalised at the scrum.
Once again it was Giles who sparked the game into life, launching a blistering attack from inside his own 22, streaking into the Treviso half and feeding Brendon Leonard but the replacement was brought down in the opposition 22 and Treviso managed to scramble the ball clear.
Giles again took the fight to Treviso with a break and chip over the Italian’s defence to gain territory after Davies had done well to run the ball out of his own in-goal area, but they could not capitalise on the break and when they were penalised within range with eight minutes to play, McKinley put the home side eight points ahead.
It was a kick that would prove decisive as Treviso ran the clock down to record a famous victory and keep Ospreys third in the table, without even registering a losing bonus point.
Guinness PRO12 Final 2017, 27th May, Aviva Stadium, Dublin.
Ticket Information: Fans can still avail of an exclusive number of €35 tickets. Book via www.ticketmaster.ie.
Further information: www.pro12rugby.com/final