Ulster Ravens coach Neil Doak has named a 27-man squad for the province's British & Irish Cup Pool C clash with London Welsh at Ravenhill on Friday (kick-off 7.30pm).
Doak said: "London Welsh are the pool leaders, they have taken maximum points from all three games.
"We always knew this would be a key game for us, we know how good they are, but we also know what we have to do to win.
"We will have to be on our guard, as the results to date show London Welsh are a quality side and can score tries from anywhere. We must have solid set pieces, win good quality ball for our backs, and go out and play a bit of rugby."
The Ravens' starting line-up and replacements will be announced on Thursday.
ULSTER RAVENS Squad (v London Welsh):
Backs (12): Isaac Boss, Cillian Willis, Paul Marshall, Niall O'Connor, Ian Humphreys, Ian Whitten, Michael Allen, Darren Cave, Tommy Seymour, Mark McCrea, Timoci Nagusa, Craig Gilroy;
Forwards (15): Bryan Young, BJ Botha, Justin Fitzpatrick, Andi Kyriacou, Nigel Brady, Neil McComb, Dan Tuohy, Ryan Caldwell, Ed O'Donoghue, Willie Faloon, David Pollock, Thomas Anderson, Ali Birch, Chris Henry, Robbie Diack.