LONDON -- But for three days' difference, they were born exactly 30 years apart. They have won six French Opens apiece. After establishing awe-inspiring dominance on clay, both managed to buck the conventional wisdom and transfer their particular brand of tennis -- an impenetrable baseline game, mental toughness and physical fitness -- to other surfaces.
And if defending Wimbledon champion Rafael Nadal can win the tournament again in two weeks' time, he and Bjorn Borg will have two more things in common: 11 Grand Slam titles and three "Channel Slams" -- the once-rare feat of winning the French Open and Wimbledon back-to-back. Borg won the double a remarkable three times in 1978-80, and it was not done again until Nadal pulled it off in 2008. Roger Federer then did it the following year, and Nadal repeated in 2010.
Borg sees his and Nadal's cross-Channel feats as all the more impressive because they have to go uphill, so to speak -- transition from their best surface to a less comfortable one in just two weeks.
"I always had problems the first couple rounds, my first or second round of Wimbledon," the Swedish legend observed a couple of years ago." If I survived those matches, then I started to play good tennis. I think it's a similarity to me and Nadal. He has a little bit more difficult [time] than Federer coming to Wimbledon.
"Federer has a different type of game, so he can get used to the courts, to the grass courts, much easier than Nadal, or for instance me, too. I had a lot of problem in the beginning."
Although their on-court personalities are very different, the career parallels between Borg and Nadal are still striking, and they have particular resonance at the moment because Nadal is pulling alongside Borg, poised to overtake the great Swede.
Should Nadal pull off the Channel Slam again this year, he will have matched just about every one of Borg's significant achievements except the Swede's five straight Wimbledons, and he can point to his U.S. and Australian Open crowns as substitutes -- two titles Borg never won, rarely playing the Australian and being continually thwarted at the U.S. Open.
There is also another, more negative subtext. This was also the period when Borg, frustrated by losses to John McEnroe at Wimbledon and the U.S. Open, would start to lose his drive for the game, then abruptly quit at the age of 26.
Earlier this season, cracks began to show in Nadal's armor for the first time as he was defeated by Novak Djokovic in four consecutive finals -- including two on clay.
"I am almost 25, but seems like I am playing for 100 years here on the tour," he said at the French Open one day, quite out of nowhere. "You don't have the chance to stop, never, you know. I think for that situation, we have a shorter career." Later, in the press room, someone remarked, "He's sounding like Borg."
It was grounds for pause, even though Nadal improved his form and his mood and went on to win the French Open. As he hoisted the trophy for a record-tying sixth time, just two days after his 25th birthday, it was difficult to imagine its being his last. Yet few imagined that Borg's sixth title in 1981 would be his last.
But surely not. This is one parallel Nadal seems determined to avoid. "I feel 25," he was insisting by the end of the French Open.
At Queen's last week, Nadal was clearly tired but was cheerful with the media. Erratic with exhaustion, he lost to Jo-Wilfried Tsonga in the quarterfinals, then headed home to Mallorca for a few days of relaxation and fishing -- first calling the tournament director on his way home to apologize for not doing better. Nadal and Borg have the same rigid professional discipline, but off the court, Nadal's lifestyle is far more sedate than Borg's.
In any case, concerns about the length of Nadal's career have never centered on his desire but on his physical health. Apart from a badly timed injury at the Australian Open, the Spaniard has been strikingly healthy for the past 12 months. He seems to have found a technique that keeps the chronic tendinitis in his knees at bay. There have been no reports of the problem since last spring and summer, when he underwent PRP (platelet-rich plasma) treatment on his knees, a process that involves injecting the patient's blood into the injured area to hasten healing.
This long stretch of fitness has allowed Nadal to rack up majors at a quick pace. Coming into the French Open last year, he was tied for 21st on the all-time list with six Slam victories. After winning four in the past 13 months, he has leaped to No. 6, and his next victory would put him tied at No. 4 with Borg and Rod Laver. Federer, on top of the list with 16 Grand Slams, will then be in sight.
But even as his legend grows, Nadal does not have quite the same aura of invincibility he did a year ago. Like Borg with McEnroe and Jimmy Connors, he has one rival, Djokovic, breathing down his neck and another, Federer, who refuses to be fully left behind. If he fails to defend his Wimbledon title, Nadal will lose his No. 1 ranking to Djokovic.
Yet instead of feeling more pressure as history beckons and the pack moves closer, Nadal believes the French Open victory will allow him to relax for the rest of the season -- one major is in the bag.
And finally, after 10 major wins, the stubbornly modest champion is prepared to acknowledge that he is one of the giants of the sport. "[One] should be humble, but not silly," he told Spanish newspaper El Pais. "With 10 titles, are you among the best in history? Yes. It's a big personal satisfaction."
Still, that was as far as he would go. "I am not the best player in history," he told reporters after the French Open. "I am one of the best. That's true. That's enough for me."
But if Nadal can carry on where Borg left off, the conversation will not stop there.
Kamakshi Tandon is a freelance tennis writer for ESPN.com.