Both fighters have the potential to win world titles and over the years they have overtaken each other time and time again, driving one another on to improve.
There was a time when they could co-exist - two young boys with a shared dream, looking to the same idols, practising the same techniques, encouraged by the same coaches - but it was inevitable that they would become rivals.
It slowly dawned on everyone that the dreams they shared were realistic - but that only one of these youngsters' goals could be fulfilled, and at the expense of the other.
Groves remembers the emergence of their collision course: "It was obvious for a couple of years that we would have to fight. We had been kept apart and only bumped into each other on the odd night. We never really spoke."
As harsh a truth as it is, it cannot be denied that in individual sports there can only ever be one winner. No matter how close the rivalry, no matter how evenly matched the men, no matter how ambiguous the outcome - it matters not. The public will not be satisfied until one man has triumphed, even if it would be fairer to merely applaud both competitors equally.
Thus it will forever be that Zale triumphed over Graziano, that Ali triumphed over Frazier, that Eubank triumphed over Benn - even though they needed each other to measure their own greatness, pushed themselves to their limits only because their rivals forced it upon them, and even though each achieved so much that it seems almost churlish to wish to separate them.
Despite how they are remembered, in each of those three cases you could not be sure that the picture would not have changed had there been one more fight. Graziano might have triumphed over Zale in a fourth match, or Frazier over Ali in a fourth, or Benn over Eubank in a third.
DeGale, the older of the rivals, began with the lead by default. Then in 2007 he fought Groves in the ABA Championship tournament. After four tense, close, two-minute rounds they each thought that they had won. It would be Groves who nicked the majority decision - for the first time he held the lead over DeGale.
Then in 2008 DeGale edged the Olympic selection ahead of Groves and went on to win a famous gold. DeGale was once more the hottest prospect, with a lucrative contract from Frank Warren to prove it.
Both turned professional within a few months of each other and built up undefeated records. In December of last year DeGale became the first to taste meaningful professional success with a commanding ninth-round stoppage of the British champion Paul Smith.
Groves had picked up the almost meaningless Commonwealth title but looked decidedly vulnerable against Kenny Anderson so it was DeGale who entered the clear favourite when Groves and DeGale faced off for the first time as professionals in May.
Once more it was extremely close and even after 12 three-minute rounds both men could legitimately think that they had won. And they did - and still do.
I had it for DeGale by one round but could see why people saw it for Groves. All in all, a draw was probably the fairest result. But people don't like draws. Even though Richie Davies did score it 115-115, Groves edged another majority decision with Dave Parris and John Keane giving him the narrowest of wins: 115-114.
No matter how close it was, Groves was happy to claim supremacy and the fans, who have never taken to DeGale, were happy to let him. I still thought that DeGale had the brighter future but on the proviso that he changed his trainer. Groves won the fight in no small measure because he has a great tactician in his corner in the shape of Adam Booth.
I assumed that Frank Warren would get DeGale a new trainer after he had lost, as he had done with Britain's previous Olympic star Amir Khan when he lost to Bredis Prescott. We've all seen Khan's incredible progress under world-class trainer Freddie Roach and DeGale, who has world-class potential, deserves the same treatment.
However, DeGale persists with Jim McDonnell.
After the Groves defeat McDonnell called the decision "absolute nonsense" adding that his 11-fight novice "has the best defence in boxing" - just as was his claim before the fight that DeGale would be a world champion in 2012.
But DeGale's jab is weak and quite bizarrely his punch technique is absolutely abysmal. It is not inconceivable that McDonnell could help DeGale make these changes, but why take the risk when there are more proven trainers available?
Groves is blessed with Booth, arguably the best trainer in British boxing today, and certainly the most imaginative. Booth fell short with David Haye's heavyweight run but Groves is likely to be more willing to work on major improvements to his style, rather than merely small tweaks.
In DeGale's next fight after Groves he laboured to a majority decision over Piotr Wilczewski, picking up the European title but still displaying the same flaws as against Groves. Still, the European title trumps the British so once more DeGale could claim domestic supremacy.
Then on Saturday night Groves knocked out Smith in breathtaking fashion in the second round. It had taken DeGale nine rounds and Smith was still on his feet when the referee took pity on him. After Groves was done with him Smith was in no fit state to continue.
Groves showed huge improvement in beating DeGale and then, by the way he crashed through Smith's defence with a well-disguised yet powerful punch, he showed still further improvement. Groves is clearly on the upward trajectory and ahead of DeGale right now, and the latter is in danger of being left behind.
Whatever happens, a rematch is inevitable, and probably more than one. Perhaps one should happen next year, just before the pair get ready to challenge at world level and then, tantalisingly, perhaps there could be a third match to unify world titles down the line.
When all is said and done, who will be the winner in the manner of Zale, Ali or Eubank? It is too close to call, and maybe it always will be, but history suggests that one of these men must emerge the victor. What is for certain is that this rivalry is still bubbling up, as it has been since 2002.
Ricky Burns put in a tremendous performance on Saturday to win a unanimous decision over Michael Katsidis.
Burns surprised many with his ability to outbox Katsidis in the centre of the ring before retreating to the ropes and covering up whenever Katsidis got past his long reach. Burns had to take a lot of punishment in the process because even if you're blocking punches with your arms you're getting hit - but the Scot did enough to take the win.
Admittedly I did think the cards (117-112, 117-111 and 117-111) were far too wide. I had it 116-114 to Burns and I could even see the case for the draw. Nonetheless Burns deserves great credit for standing up to a puncher like Katsidis, and he undoubtedly justified his move to lightweight - he looked much stronger than before, whilst still possessing good height and reach at the weight.
Katsidis said after the fight that he was simply not the fighter he once was: "I just didn't have it... if a guy would have sat on the ropes like that against me last year, I'd have biffed him out of there."
It is clear now that Katsidis has never fully recovered from the beating he took from Juan Manuel Marquez last year, having been competitive against the great Mexican, and he was soundly defeated by Robert Guerrero after that.
At this stage Katsidis may think of retirement because he has shipped a lot of punishment in his time. He deserves another payday if he wants it and a rematch with Kevin Mitchell is an exciting prospect which would draw a good crowd. Whatever he does, Katsidis deserves great respect for how he has conducted his career - he possesses the warrior spirit and the three times he has come to the UK he has put on a scintillating show.
Burns may not quite reach the top of the lightweight division, but he has now earned the right to challenge the best. Let's hope he pushes on from this performance, unlike after his previous big win against Roman Martinez when he disappointed fans by taking on three dud opponents in a row.
- Sports & Recreation