Recalled Scotland flanker Blair Cowan insists he is ready to step up and face South Africa if required this Saturday.
The London Irish forward has rejoined Vern Cotter's squad as an injury replacement for lock Grant Gilchrist, who will miss the rest of the World Cup after damaging his groin.
New Zealand-born Cowan was left devastated when he failed to make the Scots' initial 31-man group for the tournament, despite starting all five of their matches during this year's RBS 6 Nations.
He was left out of the travelling party as head coach Cotter gambled on taking just one specialist openside - John Hardie - south with him.
But his fellow Kiwi missed Sunday's 39-16 win over the United States and Cotter has now decided to use Gilchrist's departure to beef up his back-row options.
Hardie is back in training but Cowan insists he is ready to go straight into action if called upon when the Scots take on the Springboks in Newcastle with a quarter-final slot in reach.
He said: "The (coaches) know what I can do. I don't need to prove myself. I just want to come up here and be positive. Even if it's just in training, I'll just bring some energy.
"And if I'm called up to play on Saturday am I ready? Yeah - just show me the jersey."
Cowan, who qualifies for Scotland thanks to his Glasgow-born mother, feared his World Cup dream was over after missing Cotter's first cut.
"It was devastating," he said. "We all knew how close the seven role was. It was probably the tightest position in the whole squad.
"I was hugely aware (that being dropped) was a big possibility because of the performances the other boys were putting out there.
"But I've been through it all before. My career hasn't been the smoothest - it's been a bit of a roller-coaster ride so know there are peaks and troughs you can go through.
"I just had to stay on my toes. There are some tight turnarounds at the World Cup so it's inevitable that injuries would happen. Just look at Wales, they've had it tough.
"So to get the call-up is sensational. It's every man's dream. It's just a shame it comes on the back of someone hurting themselves.
"I just saw the boys when I arrived and I was kind of caught off-guard by how stoked I was to see them. I was quite emotional. I'm just excited to be part of a World Cup now."
The 29-year-old was preparing to face Harlequins with his club side on Friday night but will now hope to play a part as Scotland aim to collect their third straight Pool B win and with it a slot in the knock-out stages.
The 11-cap forward said: "I can't remember what I was doing when I got the call. I was either eating food or sitting on the couch. It's usually one of those two. I think I was just chilling after training.
"I saw I had a missed call from (team manager) Gav Scott and straight away I thought, 'This might be what I think it is'.
"I gave him a call back and he put me straight on to Vern. It didn't take long to get my stuff ready after that. You'd have just seen a dust shadow as I jumped off the couch to pack my bags."
Cowan has spent the hours since receiving his return ticket reacquainting himself with the Dark Blues play-book.
He rejoined up with Cotter's squad at their base in Newcastle on Tuesday morning after catching an early-morning flight from London.
But the head coach does not think it will take him long to re-adjust.
Cotter said: "We're all really disappointed for Grant who is an important player to the group, both as an athlete and as a decent human being.
"Blair, who comes in, was a bit unfortunate to miss out on selection in the initial 31-man group, but has shown great character to continue his work, stay fit and focussed, in case such an opportunity came up.
"He knows our systems well having spent a lot of time with this group before and during our pre-season campaign and will fit in seamlessly, and bring his freshness, leadership and enthusiasm to our training ahead of some very tough Test matches."