United Rugby Championship
Dragons (3) 10
Try: Owen Con: Evans Pen: Evans
Leinster (14) 33
Tries: Sheehan, Clarkson, Frawley, Ngatai, Penny Cons: Byrne 4
Dan Sheehan inspired Leinster to a 13th win in a row over gutsy Dragons, who saw Taine Basham sent off for foul play.
First-time captain Sheehan scored Leinster's first try and had a hand in further scores for Thomas Clarkson and Ciaran Frawley.
Dragons centre Aneurin Owen capped a promising display with a try.
However Charlie Ngatai and Scot Penny crossed either side of Basham's red card in a bonus-point win.
The Wales flanker was banished for a petulant elbow into the head of Ross Byrne that even his head coach could not defend after the match.
It was a needless offence that left his side, already trailing 26-10, down to 14 men for the final 18 minutes.
A third win in four saw Leinster move back to second place in the United Rugby Championship, behind leaders Bulls on points difference.
Dragons are now one of only two sides without a win, a point ahead of bottom side Sharks.
However, head coach Dai Flanagan was left fuming after claiming a communications breakdown meant Italian referee Gianluca Gnecchi could not hear the assistant referees in the first half, when Dragons were on top.
Both sides welcomed back a host of internationals from World Cup duty.
It meant Dai Flanagan was able to field a back row of Dan Lydiate, Basham and Aaron Wainwright for the first time, while Leinster were led for the first time by Ireland hooker Sheehan.
The Wales trio were tenacious around the field and at the breakdown, but the Irish front-rower finished a driving maul for the game's opening try on nine minutes.
However Leinster did not have it all their own way as Evans kicked a penalty and Jared Rosser went close from Owen's kick
Elliot Dee and Lloyd Fairbrother returned from facing Barbarians for Wales to the Dragons front row, but the scrums proved a bone of contention with referee Gnecchi.
It was from another penalty from the set-piece that Leinster finally broke clear with a second try just before half-time. Prop Clarkson crashed through from a clever move straight off the training ground.
Having held out for so much of the first half, Dragons were undone only 56 seconds into the second.
Rio Dyer spilt a pass in midfield, and Sheehan pounced to start a rapid counter-attack that ended with the hooker handing full-back Frawley a scoring pass in the right corner.
It was a decisive blow in what had been a well-contested match.
Dragons managed a response despite having their line-out drive knocked back when Owen raced onto Rhodri Williams' kick for their first try.
However Leinster clinched the bonus point on 62 minutes when Ngatai scored from Byrne's pinpoint cross-field kick.
It got worse for Dragons when Basham was sent off and George Nott followed to the sin bin moments later for a high tackle that left them with only 13 players for the closing stages.
Replacement Penny grabbed Leinster's fifth in added time for a defeat that extends the Dragons' winless run at home that stretches back to October 2022.
Dragons head coach Dai Flanagan said:
"We are doing some stuff that is not acceptable. We're not going to get wins unless we start performing better and eradicate the errors.
"It was very silly from Taine. He wants to be a top-end player, but that wasn't good enough and top-end players don't do things like that.
"But in the first half, we were in the game and there were no comms between the touch judge and the referee.
"We were hearing the touch judge calling infringements against Leinster that the ref hasn't given, then we found out at half-time the mics weren't working. The league needs to be better than that."
Leinster head coach Leo Cullen said:
"It was a tough and physical game and given the conditions it was about playing in the right areas and making the fewer mistakes.
"We got the early line-out drive try, but Dragons had periods on top and the two tries either side of half-time were crucial. We're delighted with the bonus-point win."
Dragons: Cai Evans; Rio Dyer, Steff Hughes (capt), Aneurin Owen, Jared Rosser, Will Reed; Rhodri Williams; Rhodri Jones; Elliot Dee, Lloyd Fairbrother, Matthew Screech, George Nott, Dan Lydiate, Taine Basham, Aaron Wainwright.
Replacements: James Benjamin, Aki Seiuli, Luke Yendle, Sean Lonsdale, Ryan Woodman, Dane Blacker, Jack Dixon, Ewan Rosser.
Leinster: Ciaran Frawley; Tommy O'Brien, Jamie Osborne, Charlie Ngatai, Jimmy O'Brien; Ross Byrne, Ben Murphy; Jack Boyle, Dan Sheehan (capt), Thomas Clarkson, Joe McCarthy, Jason Jenkins, Ryan Baird, Will Connors, James Culhane.
Replacements: Lee Barron, Paddy McCarthy, Michael Ala'alatoa, Max Deegan, Scott Penny, Cormac Foley, Harry Byrne, Rob Russell.
Referee: Gianluca Gnecchi (FIR)
Assistant referees: Ian Davies & Mark Butcher (WRU)
TMO: Stefano Roscini (FIR)
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