Warrington Wolves boss Sam Burgess waits on injured pair ahead of Hull KR semi-final

Thewlis sat out last weekend's win at Huddersfield Giants with a minor issue, while Yates has been struggling with a neck problem since Warrington's defeat to Leeds Rhinos in late March.

Captain George Williams and forward James Harrison have already been ruled out of the Doncaster showdown with the Robins, along with first-choice full-back Cai Taylor-Wray.

"We've not really done too much this week so we don't have a clear idea yet," replied Burgess when asked about the health of his squad at Tuesday's semi-final event in Warrington.

"It's probably not as positive as we thought it would be towards the back end of last week but we've still got four or five days to go so we'll get a clearer idea as we go on.

"Players like Josh Thewlis and Luke Yates are still in with a shout but they've got a bit to get through first.

"In these games, it's important that the players are ready to perform; it's not just about getting to the starting line.

"The good thing is that we've got some young lads in there who are ready to go if needed. We'll prep both ways and will see a bit later in the week."

Williams' absence puts more responsibility on the shoulders of veteran half-back Marc Sneyd, who had a spell out of the team in the early stages of the campaign.

Burgess is backing the three-time Lance Todd Trophy winner – including the man-of-the-match award in last year's Wembley defeat to Rovers – to step up when it matters.

"Sneydy obviously has been there and done it all before," said Burgess.

"He's very composed, doesn't get overawed by the occasion and I thought he was brilliant for us last year at Wembley.

"His management of the game was phenomenal. I think it'll be required again for him to be at that level on Sunday.

"Knowing Marc, he won't play the game too early. He'll just wait to see what the conditions are on the day and manage himself around that. We're looking forward to it."

Meanwhile, Ethan Havard's chances of playing in Saturday's first semi-final are over after his appeal was rejected.

Wigan Warriors challenged the prop's grade B head contact charge in the hope of freeing him up to face St Helens.

However, his one-match ban stands after a tribunal found the grading to be correct.