Given the long and grueling march Andy Murray endured to finally get to the summit of men's tennis, it seems like sweet justice that the 29-year-old Scot now gets to enjoy sitting atop the world rankings for a few weeks longer. His rout of longtime nemesis Novak Djokovic on Sunday in the year-ending ATP World Finals ensured that Murray will have top ranking until at least the beginning of 2017.

Murray has rarely accomplished anything great quickly. It's just not his M.O. But his careerlong habit of stubbornly persevering, come what may, is precisely what lifted and distinguished him in a men's tennis year that became a war of attrition by the end of 2016.

First, Roger Federer fell out, injured. Then Rafael Nadal, too. After finally winning the French Open for the first time and holding all four Slam titles at once, Djokovic abruptly hit a wall that seemed more mental than physical. Djokovic's results the past five months of his year, starting with his third-round flameout at Wimbledon, featured a series of upsets and occasional tantrums on the court that left him looking like a man sapped of self-belief by Sunday's straight-sets loss to Murray.

But it would be too easy (and unfair) to say Murray simply feasted on other people's absences or mistakes on his way to becoming the oldest first-time No. 1 since Australia's John Newcombe earned the top spot at the age of 30 in 1974. Murray is better than that.

Murray is a three-time major champion, a two-time Olympic gold medalist and a Davis Cup champ. He plays some of the best defense in the game, returns magnificently and runs down balls others don't bother to chase. The conviction it took him to physically build himself up from a string bean kid from Scotland who had some promise into an indefatigable athlete who can handle the kind of workloads he routinely endures at major events is a talent. The same goes for his ability to remain resolute as he tried and tried to crash the Federer-Nadal-Djokovic stranglehold on the top and finally succeeded, ending all that dismissive talk that the Big Four was really the Big Three-and-a-Half.

A lesser competitor would've said the hell with it a long time ago.

So it was a little odd Sunday to hear Murray say, "I never, ever imagined [No. 1] was possible" after he defeated Djokovic before a raucous crowd that cheered the Scot on and on at London's O2 Arena.

His disclaimer is hard to believe.

Murray has not only navigated an era in which the three champions in front of him hoarded 43 Grand Slam titles (Federer, 17; Nadal, 14; Djokovic, 12). He also had to carry the hopes of tennis-mad Britain on his shoulders. And at times, never more so than at Wimbledon, it was hard to know whose hovering presence was more of a burden for Murray: the ghost of 1930s champion Fred Perry, the last British man to win the All-England Club title before Murray, or poor star-crossed Tim Henman, who came tantalizingly close to winning Wimbledon between 1998 and 2002 but never did.

Last week, Murray even heard -- unfairly -- that there was an asterisk next to his year-closing rush to No. 1 because he hadn't beaten a top-five player between the US Open in September and ATP Finals week. And he was right to parry back, telling reporters, "I can only beat the people in front of me. And I did that this week."

He sandwiched career-best winning streaks of 22 and now 24 matches (and counting) around his grouchy quarterfinal loss to Kei Nishikori at the US Open. Murray finished the year with a tour-best nine titles.

His June reunion with Ivan Lendl as his coach has the same transformative effect on him that their work together the first time around did. Lendl demands that Murray play with a calm that even Murray wasn't sure he could achieve.

Looking forward now, Murray's ability to hang onto the No. 1 ranking sets up a fascinating dynamic for 2017. It should be one of the most interesting men's tennis seasons in years because of the uncertainty, the sentimentality in play and new faces involved.

Remember, Murray wasn't the only player rising in 2016 while Federer, Nadal and Djokovic slid backward or tried to stay in the top 10. Stan Wawrinka, who beat Djokovic for the US Open title, affirmed his stature as the most dangerous floater in every Grand Slam draw.

All of this was new: Milos Raonic finally showed signs of becoming a big-tournament threat, not just a big server. Argentina's Juan Martin del Potro gave fans hope that his long-running wrist problems might finally go away long enough to let him contend for majors again.

Nishikori continued to run down balls and wins like the second coming of Lleyton Hewitt, and Marin Cilic remains capable of giant-killing tears, too. Dominic Thiem, the most successful of the #nextgen players the ATP is pushing, finished ranked No. 10 but was playing on fumes by August. Hopefully, he learned a lot this year about overscheduling himself.

Nick Kyrgios is one of a group of young players who could put pressure on Andy Murray in 2017. AP Photo/Koji Sasahara, File)

If Australian bad boy Nick Kyrgios comes back from his suspension and fines for tanking an autumn match in China with his head finally screwed on straight -- a big if -- and countryman Bernard Tomic tones down his antics, too, Murray won't be the only one troubling Federer and Nadal as they try to prove once again their days as major title contenders aren't over. Even 19-year-old Alexander Zverev, the youngest player in the top 50, has the talent to break through like Thiem did this year.

But all of them have to pursue Murray now. And Murray has proved he will not be easy to catch or tire of the race.

He was only 22 the first time he got to No. 2 in the world.

It took him seven years and 82 days to take this last step up to No. 1. Murray's title win in Paris two weeks ago ended Djokovic's 122-week run at the top. Sunday's win was only Murray's 11th against Djokovic in 35 career showdowns.

Djokovic, who is also 29, has still not elaborated on the "personal problems" that he said weighed on him this fall. But he will have time to mend now, same as Federer and Nadal have.

All of them should return refreshed and ready when the tuneups for the Australian Open arrive in January.

But Andy Murray, so long the tortoise among the hares, finally has everyone pursuing him for a change.

Sunday, he shook his head when reminded of that.

"Pretty special," he said.