Cesc Fabregas had already quit the Camp Nou to become Arsenal's youngest debutant, and scorer, aged just 16 when Celtic and Barcelona began their enjoyable mini-series which by next month will have seen the teams do battle in eight games over eight years.

He left the club he adores because he was bored; bored of constantly winning games by double figures and bored of not being promoted to his ability level, pegged back by his date of birth. He was also the victim of a massive adrenalin rush when the club which was about to win the English Premiership title without losing a match asked him to play in their first team. Immediately.

When he looked in his rear-view mirror to discover Celtic had knocked Frank Rijkaard's star-studded Barca out of the Uefa Cup in 2004, thanks to Alan Thompson's goal at Parkhead and the most remarkable of 0-0 draws at the Camp Nou, it is a good bet that Fabregas didn't have second thoughts.

Yet now he is back, home and hungry, amidst what seems an almost incessant white noise of "is he good enough?", "is he doing enough?" "what's his best position?".

At Arsenal, where he enjoyed a 5-1 aggregate win over Celtic in this competition's preliminary phase three years ago, the 25-year-old Catalan just couldn't buy a trophy (ignore the Community Shield and you have one FA Cup over eight years); nor could he go more than a few straight months without succumbing to some muscle injury or another.

Once at Barca, the team where he was supposed by some to be "surplus", he immediately registered his third highest appearances in a season (48) and his second highest goal total (15), with 20 further goal assists, while beating Real Madrid three times, scoring in an away Clasico, lifting four trophies and then excelling while winning Euro 2012 with Spain as an auxiliary striker.

All this while freely admitting that each of his preferred positions are occupied by better players than him and that his lack of a proper pre-season in 2011 cost him heavily by the dog days of April and May 2012.

Whether or not he starts against Celtic, Fabregas will have a significant role to play during this potentially testing double-header. Little wonder, given all of this, that it frustrates him when there's so much ill-informed opinion spoken and written about him.

The Fabregas view? "There may be people who consider me frivolous, but it's up to them to justify why they come up with that. Maybe they are the ones who were saying I wasn't in good shape at the start of last season, when in fact I was better than ever and I finished up proving them wrong. At the end of the day people will always talk. If some guy doesn't like me, he's always going to slag me off no matter what I do.

"There have even been rumours that Pep Guardiola wanted rid of me. But he knew what he was getting when he signed me and it's absolutely untrue that we ended up on bad terms or that he didn't like me. I got on brilliantly with Pep, in fact we used to chat about England all the time, and I'll be grateful to him for the rest of my life."

In leaving Arsenal, Fabregas also left behind his partner, who he can only visit on the rare occasions when the club gives the players two consecutive days off. But that was the sacrifice he was willing to make to re-join his boyhood team-mates, Gerard Pique (with whom he used to pinch petrol caps on Barcelona beach when they were Oliver and the Artful Dodger) and the sublime Leo Messi.

"There was a price to pay for coming back to Barcelona – it's not easy to play for the best team in the world," he said. "I was the captain of Arsenal and I felt super important there. But I've never kidded myself. You have to come to terms with the fact that three of the five best footballers in the world play in the three positions that are open to me [Messi, Iniesta, Xavi]. But I don't waste time moaning about it.

"I enjoyed last season hugely: I learned a lot, I won trophies, scored in finals and scored at the Bernabeu. But for some people it seemed that the last four games [when he was hit by a scoring drought and Barca surrendered the league and Champions League] are more important than the first six.

"Last season I think that my level of fitness didn't allow me to do everything I needed to do. I arrived without pre-season training and started playing flat out from day one. I was so motivated, so determined to succeed that I wanted to do everything, but in the end it wasn't possible. At Barcelona if you're not on peak form there's always someone who is. It's such a demanding club to play for that if you're out for a while, it's a struggle to get back in. At the moment I've played the majority of the last few games, scored a few, made a few and I'm in fantastic shape."

Celtic beware.