Sam Williams grabbed a late try to ensure his time with Catalans Dragons is not over yet and end Leeds’ dreams of a Super League and Challenge Cup double.

The Dragons visited Leeds for the final play-off game of the weekend on Saturday and it was Canberra Raiders-bound scrum-half Williams who struck the decisive blow to secure a surprise 24-20 victory.

Leeds, who have already lifted rugby league’s Challenge Cup this season, led going into the final stages, courtesy of tries from Carl Ablett, Kallum Watkins and Jamie Jones-Buchanan.

For the visiting Dragons, Williams had touched down first, before further tries from former Newcastle Knight Zeb Taia and Kiwi forward Louis Anderson.

The Rhinos, who finished three points above their opponents in the regular season to earn home advantage, must have thought they have won it when Jones-Buchanan wrestled the lead from the French outfit late on.

But Williams, who joined the Dragons from St George Illawarra earlier this year, popped up to break Leeds hearts in the dying stages.

Catalans will now face one of the losers from this week’s earlier play-off games.

That means life in France is not over for Williams, who has agreed to return to Canberra, where he played between 2011 and 2013, for next season’s NRL.

Elsewhere on Saturday, Joel Monaghan’s hat-trick provoked a sharp turnaround to prevent Warrington from falling at the first play-off hurdle.

The Australian winger, top try scorer in this year’s Super League to date, crossed over three times as the Wolves beat Widnes 22-19.

Widnes had held a commanding lead in the first half as former Wests Tigers playmaker Rhys Hanbury scored, while Paddy Flynn grabbed two tries.

But it was Monaghan who had the final say, as two quickfire tries after the break completed his hat-trick and turned the game.

Former Sydney Roosters forward Mose Masoe was among the scorers as St Helens ran riot after half-time in their 41-0 thrashing of Castleford on Friday.

St Helens, who hung onto the League Leaders’ Shield despite losing their final two regular-season games, swung back into top form at just the right time.

Challenge Cup finalists Castleford found themselves 13-0 down at half-time after a pair of James Roby tries for the hosts.

And they were blown away after the break, with Masoe running in the last of five second-half scores.

That ensured St Helens are in the final four, where they will be joined by Wigan.

Wigan had outdone the Saints the previous day, running in 10 tries to comprehensively see off Huddersfield 57-4 and move into the semi-finals.

Australian-born back Dan Sarginson and former North Queensland Cowboys star Matty Bowen were among the scorers as Huddersfield were demolished.

Wigan, seeking to retain their Super League crown, were 24-0 up at the half-time hooter but they kept the pressure on after the break.

Huddersfield could only manage one consolation try through Leroy Cudjoe.