The Lampard and Gerrard question. Nothing better sums up the malaise and underachievement of England's national team in the 21st century than turning the blessing of having two world-class midfielders into an apparently unsolvable riddle.
Glory at a major international tournament, or even a genuine near miss, might have elevated the conversation surrounding Steven Gerrard and Frank Lampard above tribalism, speculation and pub debate.
But their co-existence as the driving forces of Liverpool and Chelsea teams that tangled often and memorably means that club rivalry will always hold far greater allure than their lukewarm combination for the Three Lions.
Lampard's retirement on Thursday, following a sojourn to Major League Soccer in the autumn of his career with New York City, maintained the unavoidable parallels. Gerrard called time on his playing days having turned out for LA Galaxy for the final time in November.
Before their final meeting on the field last August – a 1-0 win for NYCFC thanks to a sixth-minute David Villa goal – Gerrard spoke of a respect between the pair that had to change once they crossed the white line.
"When that whistle goes and for 90 minutes we are competing against each other, it is war," he said. "We fight against each other, we always have.
"I'm a huge fan of Frank. He's a phenomenal goalscorer from midfield. I play in the same position myself so I understand how difficult that is."
Gerrard recognised a privately educated and mild-mannered son of a football family who could go blow-for-blow on the field with his own all-action working-class hero, while Lampard last week labelled the man who famously came close to joining him at Chelsea in 2004 as his toughest opponent.
"He had everything," he said in a Daily Mail interview with Gerrard's friend and long-time Liverpool colleague Jamie Carragher. "He'd deal with you defensively and hurt you going forward."
The legacy they leave behind, purely in terms of numbers and medals, is impressive.
Thrust among a plethora of supreme strikers, Lampard is fourth on the Premier League's all-time goalscorers list with 177 – a season-long encore at Manchester City in 2014-15 lifting him above Thierry Henry.
Gerrard is the only other midfielder in the top 15, with 120 strikes, all coming with the Liver bird on his chest.
Noted for his set-piece delivery, the Anfield favourite can boast 92 Premier League assists, although Lampard is second only to Ryan Giggs in this category with 102 – a statistic that flies in the face of detractors who sought to label him as a one-dimensional performer, schooled simply in the art of timely penalty box arrival.
Lampard's role in Jose Mourinho's all-conquering Chelsea sides of the previous decade, along with the European success that came in the aftermath of Carlo Ancelotti's brief tenure, give him the edge in the medal count.
They have a Champions League and UEFA Cup/Europa League apiece, Gerrard leads 3-2 on League Cups and Lampard prevails 4-2 on FA Cups.
However, the latter was a three-time winner of the Premier League crown that eluded Gerrard – most cruelly as his old foe slipped to the Anfield turf on the opposite side of the centre circle in April 2014.
Despite Gerrard's brief and memorable stints as an emergency right-back, Lampard showed himself to be more versatile as his career went on.
It was the Chelsea favourite who slipped back into a deeper role alongside Gareth Barry, allowing Gerrard to wreak havoc from a free role on the left during England's qualifying campaign for the 2010 World Cup. Fabio Capello appeared to have briefly cracked the code that would befuddle him and his two esteemed cap centurions once more during a dismal campaign in South Africa.
The sight of Lampard becoming more of a squad player at Chelsea and an impact sub at City, while still operating effectively, spoke well of his adaptability and lack of ego. Once Gerrard's status as the main man at Anfield began to slip in the 2014-15 season, the writing was on the wall. He knew no other way and could be nothing else.
But consider those odds-defying moments in Istanbul and Cardiff. Why would he want to be anything else?
The times Gerrard guided substandard Liverpool sides towards matching the achievements of their superior predecessors should define him, not a failure to add league title number 19 to that lineage.
His show-stopping displays meant Gerrard appealed to the football romantics in a way the relentlessly efficient Lampard never could, but the pre-Abramovich signing holding his own and defining an era as the roubles rolled in underlined him as the steely competitor the Liverpudlian still measured himself against when the pair crossed the Atlantic.
Both men have their vocal champions, few of whom will be as gracious as Lampard and Gerrard still are towards each other. This mutual admiration should not be underplayed.
While the rest of us wondered aloud over their seeming inability to help one another in England colours, Lampard and Gerrard pressed diligently on with their shared ambition to be the best and a worthy rival to measure themselves against.