Dragons forward Paul Vaughan.

Paul McGregor will focus on fixing St George Illawarra's leaky defence before the finals after the Dragons failed to limit their opponents to their target of 16 points or less for the third time in the last four matches.

The St George Illawarra coach has identified 16 points as the figure his players needed to restrict teams to give themselves a chance of winning matches this season but the Dragons succumbed 36-18 to Sydney Roosters at Allianz Stadium.

After scoring three converted tries, the Dragons would have won the game if they had been able to limit the Roosters to 16 points but one-on-one misses on the edges proved costly as Latrell Mitchell and Blake Ferguson caused havoc.

"Scoring 18 points should win you a game against a good quality side, but leaking in 36 ... you can't beat anyone doing that," McGregor said. "I thought our ruck control was quite good but our one-on-one misses were quite poor and that sums it up.

"Defensively, we have to be better. Last week we made 13 missed tackles and this week we missed 36." 

The result followed a 52-30 loss to Melbourne and 20-16 defeat by Wests Tigers before last weekend’s 24-10 win over North Queensland.

St George Illawarra have also conceded more than 16 points in each of their other three defeats this season – a 20-12 loss to the Warriors in round seven, a 24-10 loss to South Sydney and in round 10 and 28-2 loss to Penrith in round 12.

Before the round-17 defeat to the Storm, they were averaging 15.6 points per match in defence but they have conceded 118 points in the past four games.

The Dragons' seventh loss enabled the Roosters to leapfrog them into third place on for-and-against as they now have a differential 46 points worse than the Tricolours.

And the Roosters, who have conceded just 263 points this season, have assumed the mantle of the best defence in the Telstra Premiership - a claim St George Illawarra were able to make before the representative period.

"It's a bit deflating isn't it," McGregor said. "The start of both halves weren't good enough, Individually we missed too many tackles and obviously paid the price. Every opportunity they got, they took and scored points.

"They were good, they came at us with speed and we didn't build any pressure, they did and when they did they scored. That was pretty much the game."

The Dragons face a Warriors side desperate to consolidate a finals berth next Saturday at WIN Stadium and McGregor will be looking for the team to start better than they did against the Roosters.

Our one-on-one misses were quite poor and that sums it up.

Paul McGregor

Starved of possession early in the match, their defence held for a while but once Mitchell crossed for the first try - a freakish effort in which he evaded three defenders to plant the ball in the corner - the floodgates opened.

Mitchell’s eighth-minute four-pointer was followed two minutes later by James Tedesco crossing from a Ferguson break and midfield kick before Cooper Cronk scored in the 23rd minute.

Ben Hunt kept St George Illawarra in the game when he raced out of dummy half to score on the last play before half-time but the second stanza was much like the first and Mitchell scored his second try in the 49th minute from a cross-field kick.

Dragons forward Leeson Ah Mau.
Dragons forward Leeson Ah Mau. ©Grant Trouville/NRL Photos

The try came in the set after Dragons centre Tim Lafai had been bundled into touch 30 metres from his own try line.

Mitchell finished the match with a hat-trick, while Tedesco got his second try in the second half and Ferguson also crossed in the 71st minute.

Tries by Hunt in the 68th minute and second-rower Tariq Sims in the 76th minute reduced the deficit.

McGregor was disappointed in his team's defence out wide, with the right edge of Hunt (4), second-rower Tyson Frizell (1), centre Euan Aitken (5) and winger Jason Nightingale (2) missing 12 tackles, while the left edge of captain Gareth Widdop (4), Sims (4), Lafai (1) and winger Jordan Pereira (1) missed 10 tackles 

 "When you say the opposition has got individual brilliance, we have got some talent in our team as well and we have got to make the tackles," McGregor said.

"The edges need to make the one-on-ones when we need to and we have got to be around the bounce of the ball when it is kicked."