St George Illawarra coach Paul McGregor has trimmed his squad to 19 ahead of the Dragons' Round 20 clash against the Manly-Warringah Sea Eagles at WIN Stadium, Wollongong.

Josh Dugan (hamstring) has been ruled out with Jason Nightingale and Kurt Mann shifting to fullback and the wing respectively.

"Josh Dugan presented with hamstring soreness post the Round 19 game against the Raiders," Head of Athletic Performance Nathan Pickworth said.

"Upon follow up scans it was determined that he would miss this weekend's game against Manly. 

"He will be reviewed and progressed accordingly over the next couple of days."

Jake Marketo is the other player to miss out on the Sea Eagles clash.

NRL Squad for Round 20 v Sea Eagles:

5. Jason Nightingale
2. Nene Macdonald
3. Euan Aitken
4. Tim Lafai
17. Kurt Mann
6. Gareth Widdop (c)
7. Josh McCrone
8. Leeson Ah Mau
9. Cameron McInnes
10. Paul Vaughan
11. Tyson Frizell
12. Joel Thompson
13. Jack de Belin
Interchange: 
14. Tariq Sims
15. Jacob Host
16. Blake Lawrie
18. Matt Dufty
19. Taane Milne
20. Russell Packer

NYC Squad for Round 20 v Sea Eagles:

1. Jai Field
2. Steven Marsters
3. Reuben Garrick
21. Dane Francis
5. Jason Gillard
6. Tristan Sailor
7. Jackson Willis
8. Stuart Mason
9. Joe Lovodua 
10. Matt Sheppard 
11. Trent Peoples 
12. Jackson Ford
13. Brayden Gallagher
Interchange:
14. TJ Uele
15. Tom Angel
16. Cooper Purcell
17. Hayden Lomax
18. Josh Dowel
19. Jack Cross
22. Bailey Dickinson