The Irish province, gearing up for next weekend's Heineken Cup final against Leicester Tigers, rested a large number of their big name players and handed debuts from the start to centre Kyle Tonetti and out-half Ian McKinley.

In a much-changed starting line-up, Ireland full-back Rob Kearney played for the first time since recovering from a bout of the mumps as he tried to keep in the management's minds for the final.

The Scarlets' midweek win over Cardiff ended the Dragons' hopes of gaining an automatic Heineken Cup place but Paul Turner's men were determined to end the league campaign with a big performance in front of their home fans.

There were five changes to the Dragons side that lost on the road at Edinburgh last week.

Gareth Wyatt, Richard Fussell and Phil Dollman were reintroduced in the back-line, while prop Adam Black and flanker Craig Hill got run-outs in the pack.

The Dragons got off to a less-than-impressive start. They failed to gather McKinley's kick-off and his fellow newcomer Tonetti almost wormed his way over for a first-minute try.

The Welsh side had to dig deep, winning Tom Willis' first lineout throw close to their line, and warding off Leinster's early advances in their 22 with some committed defending.

Kearney, playing on the left wing, was whistled up for holding onto the ball on the deck, allowing Jason Tovey relieve the pressure for the Dragons with a thumping kick downfield.

But a searing break from Fergus McFadden got Leinster back up to the hosts' 22 and hands in the ruck allowed the centre kick Leinster into an eighth-minute lead.

Tovey was off target with his first penalty attempt and after Leinster flanker Sean O'Brien was sin-binned on 17 minutes for illegally preventing a quick ruck release, the Wales Under-20 international missed his second place-kick.

The Dragons were coming more and more into the game at this stage, showing more aggression in rucking situations than the visitors and moving the ball wide with greater aplomb.

Leinster were keeping them in check though and having kept the score at 3-0 while O'Brien was off, Michael Cheika's side were beginning to build momentum.

But they crumbled badly when put under pressure by the Dragons' strong-running backs on the half-hour mark.

A chip ahead from Rhodri Gomer Davies caused the initial danger, stand-in captain Stephen Keogh failed to deal with the bobbling ball and McFadden's instinctive challenge on Tovey as the Dragons number 10 chased the ball over the try-line resulted in a penalty try and a second sin-binning for Leinster.

McFadden impeded Tovey as the ball bounced over the try-line and eventually over the dead-ball line with Tovey in hot pursuit.

Referee Graham Knox was quick to signal for a penalty try, and McFadden knew what was coming.

Tovey tapped over the simple conversion and down to 14 players again, Leinster leaked a second try five minutes later.

Leinster lost the ball forward at their own lineout, inside their 22, and the Dragons seized their chance.

They quickly slung the ball out to the right where a three-to-one overlap left Girvan Dempsey with little chance and Dollman passed for full-back Martyn Thomas to touch down in the corner.

Tovey missed the difficult conversion and Leinster managed to close the gap to 12-6, right on the stroke of half-time, with the returning McFadden just clearing the crossbar with a penalty from 37 metres out.

Neither side had played anywhere near their potential and errors, particularly with ball in hand and out of touch, continued to blight general play in the second half.

With the team changes, Leinster needed time to get their combinations working but there were some bright moments in attack from Tonetti, O'Brien and the hard-working Trevor Hogan.

The hosts, with Gomer Davies, Danny Lydiate and Andrew Hall prominent, looked the more potent but they struggled to create any clearcut chances and some frustrating knock-ons and forward passes ended their best attacks out wide.

McFadden cut the gap to 12-9 with a driven penalty from over 40 metres out, after Hall cynically blocked a ruck pass from Leinster's replacement scrum half Paul O'Donohoe.

Cheika brought on three more players to make their senior debuts - David Kearney, younger brother of Rob, Ian Madigan and Jamie Hagan.

The Dragons, with more consistency and experience in their side, had the better of the closing quarter-hour and soon put the game beyond Leinster's reach.

After McFadden missed a 67th-minute penalty opportunity, the hosts ended a long spell of possession with a successful penalty goal from replacement James Arlidge, who came on from the injured Tovey.

With time running out, Leinster shunned two kickable penalties in favour of going after tries but they never really got within scoring range.

And the nail in the coffin came with Arlidge's second penalty, struck from 30 metres out. That put the seal on the Dragons' fourth win in their last five outings against Irish opposition at Rodney Parade.

Speaking after the game, Leinster coach Cheika said: "I thought that there were some good performances out there, but in key moments in the game things didn't go our way. The effort was good and we could have won the game.

"Rob (Kearney) needed 80 minutes and he also got time at full-back which was good for him.

"We want top three finishes in the league every year and tonight was a great opportunity to give some of the younger players some game time.

"I was pleased with Kyle Tonetti and Ian McKinley, while Sean O'Brien and Kevin McLaughlin also played well."