Dubbo CYMS coach Tim Ryan has labelled this weekend's clash with Wellington at Caltex Park his side's biggest of the season so far but is backing his players to take it to the intimidating Cowboys pack.

CYMS have been top of Group 11 since late June but Wellington have roared into minor premiership contention with a run of seven wins in a row.

The last time the Cowboys tasted defeat was back in May in their first clash with CYMS but a win in Sunday's reverse fixture will see Justin Toomey-White's men leapfrog the Fishies into top spot.

The impact provided by the Wellington forward pack has been a big catalyst for their rampant attack, with the Cowboys having scored more than 100 points than any other team in the competition.

"It's one versus two and it's always a tough match against the big Wellington side but I'm really looking forward to it," Ryan said.

"They've got the size on us, we're not the biggest pack and I believe they are the biggest in the competition so we're going to have to really work hard up the middle but also out on the edges too.

"We like to pride ourselves on our defence but they've got a lot of point-scoring threats all over the park."

Luke Jenkins looks likely to miss out for CYMS as he continues to battle a shoulder injury while Blake Tremain-Cannon is only a 50-50 chance after suffering concussion and a broken nose against Westside three weeks ago.

Wellington only have the one major concern with winger Aidan Ryan a long-term injury absentee but Toomey-White did limp off after injuring his ankle during last weekend's win over Macquarie.

Toomey-White has assured his team he will play and the Cowboys are further boosted by the return of Lewis Stanley from suspension.

With CYMS only one point ahead of Wellington leading into tomorrow's clash and Macquarie and Nyngan also not far behind Ryan said his side could not afford any slip-ups between now and the finals.

"It's been so tight all year and Macquarie are not that far behind either and Wellington have really jumped up so this is the time of year you want to be hitting your straps," he said.

"Regardless if we win or lose on Sunday we've still got some work to do, Wellington have still got a bye left so I think if they win they'll secure the minor premiership but we've still got a tough month of footy left."

Sunday's match will get under way an hour earlier than usual with the under-18s kicking off at 10.30am and the first grade set to start at 1.30pm.

o DUBBO CYMS: 1 Kieran Shipp, 2 Colby Pellow, 3 Jyie Chapman, 4 Alex Ronayne, 5 John Grey, 6 Tim Ryan, 7 Daryl Cubby, 8 Ainsley Coxsedge, 9 Alex Bonham, 10 Ilisoni Vonomateiratu, 11 Ben Marlin, 12 Jordan Reynolds, 13 Matt Naden. Interchange: 14 Jopi Tui, 15 Nicholas Wilson.

o WELLINGTON COWBOYS: 1 Norm West, 2 Robbie Donn, 3 Kieran Brien, 4 Chris Jones, 5 Jake Tolhurst, 6 Lewis Stanley, 7 Trent Forrest, 8 Mick Ryan, 9 Richard Peckham, 10 Chris Thompson, 11 Justin Toomey-White, 12 Shannon Ireland, 13 Ken Everson. Interchange: 14 Nathan Thompson, 15 Nathan Smith, 16 Scott Thompson 17 Paul Black.