St George Illawarra coach Paul McGregor has named a 21-man squad for the Round 21 clash against the Newcastle Knights at McDonalds Jones Stadium, Newcastle on Saturday, July 29.

Josh Dugan (hamstring) will return to the side in the centres following Matt Dufty's solid NRL debut last weekend against the Sea Eagles.

Dugan – who will play his 150th NRL game – replaces Euan Aitken (shoulder) in the centres.

"Euan Aitken suffered a shoulder subluxation against the Sea Eagles on Sunday afternoon and underwent follow up scans on Monday afternoon," Head of Athletic Performance Nathan Pickworth said.

"Following results from those scans, we plan on consulting with a specialist to determine the best course of action. A return to play date will be determined from there."

Joel Thompson (ankle) also returns to the line-up after being withdrawn during the warm-up prior to the Dragons' win over the Sea Eagles.

NRL Squad for Round 21 v Newcastle Knights

1. Matt Dufty
2. Nene Macdonald
3. Josh Dugan
4. Tim Lafai
5. Jason Nightingale
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. Russell Packer
17. Kurt Mann
18. Blake Lawrie
19. Taane Milne
20. Jake Marketo
21. Luciano Leilua

Players unavailable:

Euan Aitken (shoulder) - indefinite

Drew Hutchison (knee) – indefinite

Kiti Glymin (shoulder) – indefinite

Siliva Havili (pectoral) – finals

Levi Dodd (knee) – season