But after missing all Ireland's warm-up games in order to build up his fitness in the gym, the Munster forward is now raring for action.
"Without doubt I've been frustrated," said Wallace, who only returned to full-contact training on Thursday.
"It's been very hard to go out and watch all the rugby sessions and you're doing all the hard, physical fitness work and you can't do the stuff you want to, and that's play rugby.
"One thing you can take out of it is that now maybe you're a bit more eager and fresher.
"You'd have a bad day and it would just get swollen or very sore and you'd think 'is it ever going to get right'.
"Even up until last Thursday - because I hadn't done any real rugby-type work on the training paddock - I wasn't sure if it was going to be okay. I went out and didn't even think about it once, I got stuck in. I was delighted with it."
Back to full fitness, the strongly-built openside is determined to use his injury-enforced absence to his advantage when the action gets under way against Namibia on September 9.
"I think at the start I wasn't that worried (of the possibility of missing the World Cup) because I've had ankle troubles in the past," he said.
"But as time went on and I had a little bit of a setback after three or four weeks, I did start to get a bit stressed about it.
"But it was always making steady progression after that. I was always hopeful that I'd make it.
"I put a lot of faith in the Ireland medical staff here and they were very good."