However, he insisted the outside-back would be fit for next weekend’s Challenge Cup semi-final against Hull KR, when the Wire squad is set to be further boosted by “a couple” of returns.
With Cai Taylor-Wray ruled out for six weeks following ankle surgery, Thewlis had been expected to deputise at full-back but was a surprise absentee from the teamsheet at the Accu Stadium.
His absence allowed youngster Lachlan Webster to make his full Super League debut and he impressed during The Wire’s 34-4 Round 10 victory.
Burgess expressed his pride in the Warringtonian teenager, who stepped in at late notice after Thewlis hobbled out of Friday’s final training session, but confirmed he expected his more senior star’s absence to be a temporary one.
“He just had a bit of a niggle in training so he wasn’t going to make the game,” Burgess said of Thewlis.
“Lachie has been in and around the group but today, he earned a lot of trust as he had a really solid game.
“He took his moments well to get out of the in-goal a couple of times, make his catches and he was sound defensively.
“I’m really proud of him – he did a wonderful job considering he only had half a session of prep.”
When asked whether or not Thewlis was in doubt to face the Robins in Doncaster, Burgess replied: “He’ll be okay for next week – it’s been lingering a bit over the last few weeks so the week off will be good for him.”
Burgess also confirmed that no fresh injury concerns had been picked up during the win in West Yorkshire, with Luke Thomas confirmed to have passed a late head injury assessment that ended his evening early.
And numbers are set to be boosted for the monumental last-four clash, with forward Luke Yates named as a potential returnee.
“Everyone’s come through well, which is good,” he said.
“With Luke Thomas, I think it was a mouthguard activation – that’s what I’ve been told but he’s fine and passed his HIA. It’s just one of those where the mouthguard was flashing.
“There will be a couple of guys back next week – I’m not sure exactly who but there will be a couple.
“Luke Yates is one who will be a chance.”