O'Connell's chest infection prompted Joe Schmidt to shuffle his deck with Tuohy promoted to the starting line-up where he featured alongside Devin Toner in the second row. Another member of Ulster's powerhouse pack, Iain Henderson, was added to the bench.
Tuohy's Ireland career began in the summer of 2010 and his seven caps prior to the Scotland game had all been won on foreign shores - New Zealand (four Tests), Australia, America and Canada.
So, O'Connell's absence handed the Ulster lock his first Six Nations start and his home debut in Dublin. They were big shoes to fill but Tuohy was confident of stepping into the role.
"I had my porridge in my hand and John Plumtree asked me to have a quick chat. I thought he was just going to go over my role for the bench and make sure I was clued up on everything and then he said I'm in," revealed the 28-year-old.
"These things happen. I played last week for the Wolfhounds, so I was very comfortable with Joe's systems. I was prepared all week for coming on early if I had to. I felt I did that all week and that gave me confidence starting today."
The tough-tackling Tuohy and the Irish defence held firm against the valiant Scots who probed throughout the first half but were limited to just three points at the interval.
"We spoke about it half-time, just keeping hold of the ball basically, building our phases. We have enough to score tries and put them away.
"It's just about keeping hold of the ball. We defended an awful lot in the first half, but it's credit to us - we only shipped three points in the first half."
The Six Nations newcomer drew plaudits from both Schmidt and stand-in captain Jamie Heaslip who felt he really stepped up to the plate and delivered a performance.
"Dan came into the starting line-up and Iain came onto the bench. Great credit to those two guys the way they adapted quickly," said the Ireland head coach.
"I thought Dan did really well stepping in, got in a fair few tackles. He will be looking for improvements in his game but that is good."
Heaslip explained: "It was a big shock to us about Paulie, we watched lineouts at 7pm on Saturday night with him.
"He had given us really good direction during the week, so we had the knowledge and then we had to bring the physicality and intensity, and we managed to do that.
"It's a big shame to lose a character like Paulie, a great leader and an inspiration. But credit to Dan who had a great game, and will give Joe a good (selection) headache."
Ireland showed against New Zealand in November that top class opposition can bring out the best in them, and Tuohy believes there is more of the same to come.
If there is a warning for Schmidt's charges it is how the 2013 Six Nations unfolded. Ireland made a great start last year, beating Wales in Cardiff, but then failed to build on that win and ended up finishing fifth overall.
"I think there's always more we can squeeze out of it. I think Wales will be a different kettle of fish next week. They had a bit of a feeler game against Italy," added Tuohy.
"Look, we won the first game last year and we all know how that ended up, so it's important to back up the first week and become a consistent team. The six-day turnaround is not ideal, but we'll roll up our sleeves."
That consistency is something Tuohy and the Ireland squad are looking to display on a regular basis, transferring their provincial form onto the international stage in the process.
But despite his relative happiness with the round 1 victory, Tuohy knows the Welsh pose a greater threat. He has played against most of them with Ulster but feels once they put on the red jersey, they are a completely different proposition.
"As soon as they put that red jersey on, they turn into a different beast. They're seriously proud of playing for Wales and they really do lift the intensity when they're playing for Wales. They're littered with Lions, so they should be high on confidence.
"It's up to us to stick to what we know, what we can do well and worry about ourselves rather than worry too much about Wales.
"(Another win) would set us up nicely for a Triple Crown away to England. But Wales at home, England away, France away - there are a few tough games coming up!"