David Ospina can pinpoint the moment when his destiny was shaped. Arsenal’s Colombia international was a 10-year-old hopeful at Club Deportivo in his home town of Medellín and, like many youngsters who show a natural aptitude for football, he played as a striker. One day, though, the squad’s two goalkeepers cried off and the coach, Dario Castañeda, put out the call for a volunteer. Ospina raised his hand.

“I was very small at the time. In fact, I was the smallest person on the team,” Ospina says. But he has never been a player to lack the courage of his convictions. His baptism between the sticks went well and Castañeda encouraged him to give the position a try over the following two weeks. It continued to go well and, it is fair to say, Ospina has not looked back since.

“It was all about being there at that specific time and specific place,” Ospina says. “After that first training session, the coach said he could see that I had the necessary attributes to play in goal. And, after those two weeks, it became my position.”

The ability to adapt and bend circumstance to his will has underpinned Ospina’s professional career, initially as a 17-year-old who was thrust against a backdrop of scepticism into the first team at Atlético Nacional – one of Colombia’s biggest clubs – and, more recently, at Arsenal, to where he moved from Nice last July.

He had joined the French club from Nacional as a 19-year-old in the summer of 2008 to replace Hugo Lloris, who had left for Lyon, and Ospina talks of how he had to “start from scratch”, and not only because of the differences in language and culture. “People didn’t know who I was, they’d never seen me play,” he says.

It was slightly different at Arsenal. Ospina was one of the stars of Colombia’s bolt to the quarter-finals of the World Cup last summer – they lost to the hosts, Brazil, on a tumultuous night in Fortaleza – and that only added to the frustration he felt over his first five months in England.

Ospina made only two appearances for Arsenal in the first half of the season: against Southampton in the Capital One Cup exit on 23 September and Galatasaray in the Champions League one week later, when he came on as a substitute after Wojciech Szczesny’s sending-off. He suffered thigh damage against the Turkish club which would rule him out for almost three months. The problem, according to Arsène Wenger, was that he had not been able to warm up properly.

Ospina said Wenger had told him he would begin the season as Szczesny’s understudy. “When I signed, he was very clear on that with me. But in my mind I was coming to Arsenal and I wanted to show what I could do.”

Ospina is not used to being on the bench. Since his breakthrough at 17 with Nacional, he has almost always been a first-choice selection. “In truth, when you get used to playing all the time and being on stage, you always want to do that,” Ospina says. “And so, when it’s not like that, it is a difficult time. But I think that when you are going through difficult times, you have to ensure you are working twice as hard and you are always prepared. You have to hold your head up, too. You can’t be moping and all downtrodden. You need to be prepared in training during these difficult moments and just be ready to grasp any opportunity when it comes.”

Ospina’s came after Szczesny had suffered his horror show in the 2-0 defeat at Southampton on New Year’s Day; the Pole was at fault for both goals and then again in the shower area of the dressing room afterwards when, his head still scrambled, he decided to light up a cigarette. Wenger had already planned to start Ospina in the FA Cup third-round tie against Hull City on 4 January but the key moment came when he stuck with him for the Premier League fixture against Stoke City the following weekend.

Ospina has started in all of the league and Champions League matches since then, with Szczesny playing in the FA Cup and helping Arsenal into the semi-finals, where they face Reading at Wembley on 18 April. Wenger started his back-up goalkeeper, Lukasz Fabianski, in every round of the club’s successful FA Cup run last season and Ospina stands to miss out on one or, possibly, two Wembley appearances this time. Having won the No1 jersey, that may feel a little strange to him.

Facebook Twitter Pinterest David Ospina, photographed at Arsenal’s London Colney training ground. Photograph: Felix Clay for the Guardian

What shines through in Ospina’s first interview with a British national newspaper, though, is his calmness. Some goalkeepers are extrovert, even a little crazy, but there is nothing loud or remotely big-time about this one. Ospina has long relied on his even temperament, from the moment he made his debut for Nacional against Cúcuta in 2006 and the media were, to put it politely, wondering who he was.

“There was a lot of pressure from the press,” Ospina says. “Nacional had always had really seasoned goalkeepers and they were already criticising the fact that here we were with a 17-year-old in the team. It was huge for me and very emotional, because Nacional was my team. I had always supported them. But thanks to God, everything went well and I was able to carve out a name for myself.”

Ospina was a prodigy. The Colombian domestic calendar is split into two championships, one for the first half of the season and one for the second and, in 2007, Ospina and Nacional won both. At 16 he had been a non-playing member of the Colombia squad at the Under-20 World Cup – they lost in the last 16 to Lionel Messi’s Argentina, who would go on to win the tournament – and at 18 Ospina made his full international debut against Uruguay.

The coaches at Club Deportivo could see he was destined for a professional career, none more so than Alexis García, a former Colombia midfielder, who led Nacional to the Copa Libertadores in 1989. García is from Medellín’s tough Chocó department and he founded Club Deportivo, a training school for youngsters, partly out of a desire to give something back. Ospina joined, aged seven and he would train on Tuesdays and Thursdays and play matches at weekends.

García took him under his wing. “Alexis and his family were so welcoming to me,” Ospina says. “I even went off with them to what are known as holiday houses. We’d still train and Alexis and his brothers would have penalty shootouts with me in goal. They’d make little bets with each other but they could not score past me. I would have been 10 or 11 at the time.”

It is a nice image: the great Alexis García struggling to beat a little kid from 12 yards. Ospina says he grew between the ages of 12 and 15, and he would eventually reach 6ft, although he is not exactly towering in goalkeeping terms. “No one ever said to me that I was too small to make it,” Ospina says. “You have to place yourself in the context of the Latin American game. Goalkeepers aren’t that tall – they might range from 179cm to 185cm. Nowadays, kids are just really tall for some reason but that wasn’t the case at the time.”

Ospina played in Colombia’s Pony Fútbol championship, an annual under-13s event which attracts massive crowds and media coverage, before he emerged through ultra-competitive trials to win a place on the Antioquia regional team. He starred in one tournament for them, saving penalties in shootout wins in the semi-finals and final, and it led to him being picked by the Colombia Under-15s. Nacional then took him, aged 14. “It’s true to say that a lot came to me early in my career and I had to grow up very quickly,” Ospina says. “Nacional is a team with a lot of pressure and it’s a team that has to win titles. You need to have your head really well screwed on when you start getting the fame and all the rest of it.”

Ospina will never forget the World Cup. No Colombian will. There were so many special moments, from the spine-tingling a cappella continuation of the national anthem by Colombia supporters before the first match against Greece to the pleasure Ospina got from seeing his brother-in-law, James Rodríguez, take the tournament by storm. Rodríguez, who is married to Ospina’s sister, Daniela, signed for Real Madrid shortly afterwards. Daniela also has the sporty gene. She now plays for Real’s volleyball team.

“Who is James Rodríguez? Who is he?” Ospina says with a smile, slipping into English for the only time during the interview. “We were very pleased with how the World Cup went but, at the same time, with the players we had, we felt we could have gone that bit further. It was frustrating to lose to Brazil. But, of course, we were proud and obviously happy with all the doors that opened for us afterwards.”

It has taken a while but Ospina is finding his groove at Arsenal. Since the Cup tie against Hull, he has kept seven clean sheets and conceded only eight goals in 12 matches. There has been a quiet authority to his game. His favourite moment so far? “The day that I arrived,” he says, without hesitation. It was when the scale of the club hit home. Ospina senses possibility.