The old "welcome to hell" straplines about Turkish football flicked into mind again at the weekend, when photos of a Fenerbahce player getting clocked with a hail of missiles from Besiktas fans - coins, water bottles and old mobile phones among the projectiles of choice, apparently - should have served to remind Chelsea of the potential volatility which awaits in Istanbul tomorrow night.

Still, the Blues' international elite ought to be streetwise enough to be able to cope with any amount of hostility, given the way they comfortably silenced a deafening Athenian crowd at Olympiacos in the previous Champions League round. No, what may concern them rather more is the display of the victim - Fenerbahce's brilliant captain, Alex de Souza.

For the reason the Besiktas fans targeted the Brazilian during the top-of-the-table derby was obvious enough by the time the night was over. In between the missiles at their rivals' Inonu Stadium, Fenerbahce's champion picked himself up and scored the two goals which have given the champions a crucial lead in their title defence.

Once again, it proved what everyone in Turkish football has long known; that this 30-year-old is by a distance the finest player in the country, one of the global game's few concealed treasures because he neither plays for his national team nor graces one of Europe's more celebrated leagues.

Take this testimonial about a man who hasn't pulled on the Brazilian jersey since 2005: "Right now, Alex is Brazil's most important footballer". Coming from a man who once really was Brazil's most important footballer, it's an observation worth heeding. For Zico ought to recognise a decent playmaker when he sees one.

Sure, there are other reasons for Chelsea to treat this trip to the Sukru Saracoglu stadium with circumspection. There's the astonishingly passionate home support, 50,000-strong, who, even Zico concedes, could make a fanatical Brazilian crowd resemble trappist monks. Then there's the bloke who supposedly fancies becoming a trappist monk, Mateja Kezman, an old misfiring Blue now scoring for fun and with something to prove.

More than anything, though, Chelsea have to be wary of how Zico, who's transplanted the messianic aura of his wondrous playing career into an infectiously enthusiastic reign as Fenerbahce coach, has combined so sweetly with Alex to bring out the best in one of football's nearly men in a team which has brought Brazilian brio to the Bosphorus.

It's no coincidence that the 'Yellow Canaries' have soared to new heights - after last season's League and Cup double, they've now become only the second Turkish club after Galatasaray in 2001 to reach the Champions League quarters - since Zico teamed up with the player he now rates as the "most intelligent" he's ever worked with.

The fabled No10 must have seen shades of himself in Fenerbahce's wiry No20. For while even his greatest admirers wouldn't dare suggest Alex's shirt number means he's twice the player Zico was, they'll point to his supreme dead-ball skills, dribbling ability, visionary passing and remarkable goalscoring prowess for an attacking midfielder as being just a little Zico-esque.

Signed for a bargain £3million from Cruzeiro, Alex was a hit at Fenerbahce even before Zico arrived, twice being voted the most valuable player in Turkey, but question marks still existed over his temperament amid the belief that, with the pressure on, his dream left foot didn't deliver.

Indeed, the same criticism finally saw him ditched from the Brazil side in late 1995 after 48 appearances.

Yet Zico's nurturing of and complete trust in the artist - "He needs a coach capable of handling him . . . he deserves his chance with the national team," he says, - has succeeded in cajoling serious big game orchestration from Alex, from Inter Milan's humbling at the start of their Champions League campaign to last Saturday's double. In total, he's scored 93 goals and created just as many others, in 185 games. That's what a legend can inspire. Just as Joe Cole revealed this week how he so loved watching videos of Zico that he put his image on his computer screen-saver, young Alex grew up with the Flamengo legend as his hero. "He was the greatest of my generation. Even today, when I go training, I can't believe I am working with my idol," he says.

Last week 55-year-old Zico became a grandad, a fact he muses upon happily in his website which gives some idea of why he's still so widely adored. For his gentle musings about football and the universe, his travelogues from London to Tokyo, his photos of himself with sweetie-bearing fans, posted under his more prosaic real name of Arthur A. Coimbra, all tell of a man with both the common touch and a lust for life.

Yet to his 25 million new subjects at one of Europe's most feverishly supported clubs, he can never play the common man. To them, Zico remains simply 'Kral Arthur' - King Arthur. Which presumably makes Alex their Sir Lancelot. Chelsea really do have competition in their endless quest for club football's holy grail.