Messi took to the field in Barcelona's Champions League semi-final first leg at Stamford Bridge last night [Wednesday] having scored a jaw-dropping 63 times for Barcelona this season.
But the Blues were both the Catalans' and their star player's nemesis again as they won 1-0 to extend Messi's goalless streak against them to seven matches.
Unlike defensive cohorts John Terry and Ashley Cole, Cahill was facing the man some regard as the best player ever for the first time, and the former Bolton star responded with a career-defining display.
"You're always trying to prove things to yourself," the England centre-back said.
"It's nice because I made the step up to international football, so I felt I could do that from the games I played with England.
"The experience I have taken from this will be vital for my career going forward."
Last night was just Cahill's second Champions League start, with David Luiz having been an ever-present in the competition this season until suffering a hamstring injury.
That may have proven a blessing in disguise, with Terry and Cahill almost impassable every time they have played together.
"It was a fantastic experience for me because I need experience in this competition," Cahill said.
"It was great to play a part and get that experience.
"If you asked most of the players, they would say they knew how big this game was going into it. There was that aura of how big the game was.
"We will enjoy it but we know it will be really tough away from home."
Although Chelsea were magnificent in carrying out caretaker manager Roberto Di Matteo's game plan, Barca created more than enough chances to have spoilt their party.
"I'm sure if you ask them they would have felt frustrated," Cahill said.
"If we can do that in the away leg, that would be fantastic, and replicate the result, it would be unbelievable.
"We are under no illusions. It is obviously going to be very, very tough against them."
The sheer size of the playing field is what makes repeating yesterday's shutout look so implausible at the Nou Camp.
Chelsea almost certainly must score there to progress, something they have fortunately managed in most of their visits.
"We probably do need to score," Cahill said.
"But if play defensively like we did as a whole team then maybe not.
"During the 90 minutes, we will get a chance.
"I have never played there but the lads say the pitch is massive. Playing them on any pitch is tough, but playing them at home is going to be really tough.
"But if we all put in performances like we did, we won't go far wrong."
The size of the pitch will also work in Chelsea's favour when they attack, especially if Didier Drogba proves as clinical as he did last night.
"He's in great form, the big man," said Cahill, who was glad to be on the same side as the Ivory Coast striker.
"When I played Chelsea before, I was never on the end of a positive result.
"He had a hard job playing up front on his own and at times he was a little bit isolated.
"I thought he did brilliantly for us - and defensively, he helped out with the number of times he was in the box next to me clearing headers away.
"He's obviously up there with the best forwards in the world when he's in that form."