When Cristiano Ronaldo appeared on stage at his Real Madrid unveiling on 6 July 2009, he was greeted by over 80,000 fans at the Bernabeu desperate to get a glimpse of the world's most expensive footballer.

His debut in the famous white shirt could hardly have been more of a contrast, though.

Two weeks later, on 20 July, he was in the town of Tallaght in south Dublin. Irish Premier Division side Shamrock Rovers, a team which included a number of part-timers, were his opposition.

"It was an agent who set it up," Jonathan Roche, Rovers chairman at the time, tells BBC Sport.

"Madrid were training at Carton House, a base in Dublin, and the only club it would be appropriate to play was us. They hadn't signed Ronaldo at this point; that made it even bigger."

'We had to ignore the build-up'

Rumours abounded that one of the biggest clubs in the world were coming to Tallaght - but initially, even the players did not really believe it.

"We read it in the papers first, and everybody was saying, 'nah, it won't happen, it won't happen'," former striker Padraig Amond recalls.

The Hoops had only recently moved into a new stadium and a new area after 25 years of groundsharing, but it was still under construction, so temporary seats were required to cope with demand for tickets.

Nearly 12,000 fans were in attendance, raising the capacity from 3,000. Tickets sold out in no time, while Sky Sports cameras broadcasted the game to the United Kingdom.

Rovers' manager was Michael O'Neill, who went on to be Northern Ireland boss and is now in charge of Stoke City.

Shamrock's Eric McGill was up against former Manchester United defender Gabriel Heinze

At the same time as preparing for this high-profile encounter, the Irish domestic season was in full swing and Rovers were in the middle of an ultimately successful title charge. Only 48 hours earlier, they had faced Sligo Rovers.

"We had to ignore the build-up, and we were left open for massive criticism if we didn't turn up for the league game," Amond continues.

"The club was always going to make money out of Real Madrid regardless of the result. That game was about the title race and making sure we didn't take our eye off the ball. But we won the game."

'I took the ball and Ronaldo with it'

Matchday arrived and the excitement was palpable. Ronaldo would start the game alongside Raul, Marcelo and Guti, while another debutant, Karim Benzema, came on at half-time. The different worlds soon became abundantly clear to defender Pat Flynn.

"They arrived in this really glamorous team bus. I work for Coca-Cola, so it was quite a picture, me parking up next to them in my van," Flynn laughs.

In the dressing room, O'Neill was relaxed before kick-off.

"He was just having a laugh with us," Amond says. "He was looking at the team sheet and saying, 'lads, what more am I supposed to say to you? It is Real Madrid. Just enjoy it.'

"We were going through who was marking who in the dressing room. The team sheet had all the official names, and obviously the Brazilian and Portuguese players often play with nicknames on their shirt.

"We didn't recognise one of them and thought he must have been a centre-half. It was only when he were stood in the tunnel that we realised it was Pepe!

"He was in the middle of serving a 10-game ban [after a red card against Getafe the previous April], but because it was a friendly, he was allowed to play."

Just minutes into the game, Flynn clattered into Ronaldo, upending the main attraction of the day.

"People were talking up the idea of me against him, and me as some kind of hard man. I'm not even sure if that is true or not," he says with a chuckle.

"One of the papers put a picture of me with blood running down my face next to him looking all pristine.

"But I played right-back and he was right-wing, on the opposite side. He came inside and took three of our players out of the game. He got to me, the ball was there to be won. I took it and him with it; it was a great tackle and feeling. He just looked and thought, 'What just happened?'"

Ronaldo was upended in the early minutes of the game by defender Pat Flynn

'The stars just aligned'

The game was goalless for 88 minutes but Real Madrid eventually prevailed 1-0 through Benzema's late winner. Real made their only moment of true quality pay, with Ronaldo substituted after a rather ineffectual first-half performance, during which he was constantly booed by the home fans.

The players' attention quickly turned to shirt swapping.

"There were loads of the lads asking for Ronaldo's," Amond remembers. "But he kept it because it was his debut.

"I saw Raul fiddling with his captain's armband just before half-time and thought he was coming off so I asked for his shirt. He said yes and gestured for mine; I had to tell him I'd be playing the second half.

"At full-time, there was a knock on the dressing-room door and Raul was there asking for my shirt. I don't know if he needed something to clean his car with or something!"

Over a decade on, Shamrock Rovers are still reaping the rewards from that day, re-establishing themselves as a force in Irish football and becoming a more regular fixture in Europe, too.

"The stars just aligned. It could never happen now," Roche concludes.

"It was more than a friendly, it implanted our brand on the new stadium. We brought Real Madrid here and it showed what a football club can do for an area."