Born only a week apart and brought up as tennis prodigies who later turned into stars, Novak Djokovic and Andy Murray have been crisscrossing the globe together, growing as familiar with each other as they are with the kid next door.
Their next run-in comes Monday, with nothing less than the U.S. Open title at stake.
OK, so it's not Rafael Nadal vs. Roger Federer — the rivalry that has defined much of the last seven years in men's tennis. But there is plenty of history. These 25-year-old players first met on the court when they were 11.
"I lost that match," Djokovic said.
But now he is going for back-to-back titles at Flushing Meadows and his sixth Grand Slam title, while Murray is trying to avoid joining Fred Stolle, the Aussie tennis great of the 1960s, as only the second man to lose his first five Grand Slam finals. If Murray breaks through, he'll be the first man to bring a major championship back to Britain since Fred Perry in 1936.
"I know how hard these opportunities are to come by," said Murray, who is in his second straight Grand Slam final and also sandwiched an Olympic gold medal in between.
This marks the first Grand Slam final not to feature either Federer or Nadal since the Australian Open in 2011 — the only other time Murray and Djokovic have met for a major title.
"It's probably the best rivalry we have in sport," Djokovic said of the Federer-Nadal matchup. "But it's also good for tennis to see different faces in the finals of a Grand Slam. I don't mind, to be honest. I'm sure we will deliver some good tennis for the people."
They have a history of that.
Djokovic opened his Grand Slam season by winning the Australian Open in a 5 hour, 53 minute match over Nadal that went down as the longest Grand Slam singles final in the history of pro tennis. Somewhat lost in all that was that Djokovic was coming off a five-set win over Murray in the semifinal that lasted 4 hours, 50 minutes.
"It was difficult in both a physical and mental way," Djokovic said. "A lot of long rallies, and you couldn't really say who was going to win that match up to the last point. Most of our matches that we played against each other were very close, and only small margins decide the winner."
Their most recent meeting was a 7-5, 7-5 win for Murray in the Olympic semifinals that cut Djokovic's lead in their all-time series as professionals to 8-6. Murray went on to defeat Federer for the gold medal.
"I guess there is no clear favorite," Djokovic said.
While Djokovic (DOB: May 22, 1987) clearly has the experience edge when it comes to winning on tennis' biggest stages, Murray (DOB: May 15, 1987) will come into Monday's meeting the better-rested player.
The Brit closed out a five-set victory over Tomas Berdych on Saturday afternoon before the weather got bad. Djokovic started his semifinal match against David Ferrer, and in blustery conditions he called the worst he'd ever played in, he fell behind 5-2 in the first set.
Play was stopped with a storm approaching the area. On Sunday morning, they returned to the court. Under bright sunshine with only a wisp of a wind, Djokovic dominated en route to a 2-6, 6-1, 6-4, 6-2 victory. This will be the fifth straight year the U.S. Open has not ended on schedule.
"I don't feel any problems physically," Djokovic said. "It was good to have the job done in four sets today. I feel fresh as I can be at this stage of the tournament and looking forward to tomorrow."
A bit after Djokovic finished Sunday, Murray came to Flushing Meadows for a short work out under the eye of his coach, Ivan Lendl, the last man to lose his first four Grand Slam finals. Lendl, of course, went on to win eight Grand Slam titles and etch his name among the greats in the game.
Murray has been among the top four in the rankings for all but a few weeks over the past four years — and a consistent presence in the semifinals of the majors, as well. But he has yet to break through, the way his coach finally did. The top three players, Federer, Nadal and Djokovic, have won 29 of the last 30 Grand Slam titles.
"I know how tough it is to beat the top, top players in big matches," Murray said. "I've had some tough losses against him. But I've also had some big highs, as well."