Barcelona forward Lionel Messi has already won everything he can at club level and on an individual basis. But the World Cup gnaws at him.
World Player of the Year awards, six La Liga titles, three Champions Leagues and a mountain of goalscoring records only begin to tell the tale of the extraordinary career of a player who is still only 26.
However, there is one thing missing from Messi's trophy cabinet; a major international triumph with Argentina.
Messi has made his name with Barcelona, who spotted him as an 11-year-old and agreed to pay the $900 a month for his growth hormone treatment if he moved to Spain.
The rest is history. Messi has grown into greatness and says he is ready to finish his career at Barcelona.
But while nobody disputes the global drawing power of the Champions League, a title on the world stage is the one achievement that continues to separate Messi from the game's all-time greats such as Diego Maradona and Pele.
This will be Messi's third World Cup. In 2006 as a raw 18-year-old he scored his only goal in the competition so far, but was not given much chance to shine by Argentina coach Jose Pekerman. He did not even make it off the bench as Argentina succumbed to hosts Germany on penalties in the quarter-finals.
Four years later in South Africa, at the same stage and against the same opponents, the circumstances were far different.
Messi arrived at the tournament with a reputation and showed it too as, without finding the net, he led an Argentine side under Maradona's tutelage through the early stages in fine style.
However, Germany counter-attacked to perfection in the last eight to hammer Maradona's unbalanced side overladen with offensive talent 4-0 in Cape Town.
This time, despite Argentina's undoubted strength in attack, coach Alejandro Sabella appears to have found a semblance of equilibrium as they emerged top of an extremely strong South American qualification process.
The key, though, will still be whether Messi can bring his best form to the biggest stage and dispel any doubts that he is one of the greatest players of all time.
Comparisons with Maradona's crowning glory in leading Argentina to their second World Cup in 1986 are hard to ignore. Maradona was 25, in the prime of his career at the top of the European game with Napoli.
Messi will turn 27 during the tournament and given his side's relatively soft draw through the early stages, will surely never get a better opportunity to end his country's 28-year wait for a third world title.
"Messi doesn't need to win a World Cup to be the best footballer in the world," Maradona claimed in a recent interview with Argentine newspaper La Nacion.
"To win a World Cup would be amazing for Argentina, for the fans and for Leo. But a World Cup more or less will not take away any of the merit of what he has done to get to where he is."
However, history tends to judge those who succeed in World Cups more favourably.
Alfredo di Stefano, Ferenc Puskas and Johan Cruyff all had arguably better club careers, but are regularly placed below Pele or Maradona in polls of the greatest of all time.
Messi's legacy would be richly enhanced by lifting the famous gold trophy in enemy territory in Rio de Janeiro on July 13.