After a two-year absence Novak Djokovic is back as world No 1.
His return to the highest peak of men's tennis was confirmed, somewhat ironically you may argue, by the withdrawal of long-time rival Rafael Nadal at last week's Paris Masters with an abdominal injury.
Earlier this season it was the Serb who had appeared a shadow of his former self as he suffered uninspiring defeats against world No 109 Taro Daniel and Benoit Paire at Indian Wells and Miami respectively.
Such results left Djokovic in a state of perplexion. A gruelling fourth-round exit to Hyeon Chung at the Australian Open had acted as the final call to undergo surgery to cure a troublesome elbow injury, which had forced him to miss the second half of 2017.
His disappointing performances on the American hard courts spelled the end of his collaboration with Andre Agassi and before too long he had decided to bring back former long-time coach Marian Vajda and trainer Gebhard Phil-Gritsch.
But despite the pair reuniting, the results were not immediate. Further early defeats against Kei Nishikori, Martin Klizan and Kyle Edmund followed on the clay courts. This was not the man who in 2016 had completed the career Grand Slam by winning the French Open.
The aura had gone and Djokovic, in May, blamed his decline on a premature return to the game but despite conceding his confidence had been hit, he insisted his desire and most significantly his belief to return to his best were undiminished.
A run to the Rome Masters semi-finals, where he lost to eventual champion Nadal, was followed by a shock four-set defeat to world No 72 Marco Cecchinato in the French Open quarter-finals. A rattled Djokovic threatened to skip the grass court season.
Fortunately for him he decided against such action. The rest is as they say history.
Defeat in the final at the Queen's Club against Marin Cilic was a hugely positive step in the right direction.
It marked the start of a period of near invincibility which saw him win back-to-back Grand Slam titles, become the first man to complete the Career Golden Masters and suffer only two defeats spanning a period of six tournaments.
Djokovic was pushed to the limit by Nadal in the Wimbledon semi-finals - a five-set thriller which overlapped two days. There was no doubting, the mental scar tissue from earlier in the season was being healed.
"I'm just overwhelmed," Djokovic said after winning the 52nd meeting between two of the sport's all-time greats.
"It's very special. It was very clear that very few things separated us. This kind of match is what you live for, you work for."
A physically and emotionally drained Kevin Anderson was no match in the showpiece as he won his first Grand Slam in two years, with his son Stefan stealing the show in the Centre Court box as he gave his acceptance speech.
Despite suffering defeat against an inspired Stefanos Tsitsipas at the Rogers Cup in Toronto, there was not a significant setback to his confidence.
A history-making victory against Roger Federer saw him win the Cincinnati title, at the sixth time of asking, but the victory was all the more significant for him becoming the first player to win all nine Masters titles.
Next on the agenda was a trip to Flushing Meadows and after a testing first week, notable for oppressive heat, Djokovic settled into a rhythm. Former champion Juan Martin del Potro appeared a stern examination in the final but not even the giant Argentine could power through his formidable resistance.
What had inspired him to back-to-back Grand Slam wins? The answer lay with a five-day hike in the mountains of the south of France with his wife, following his French Open defeat to Cecchinato.
"We sat down and we just looked at the world from that perspective," he said.
"I breathed in the new inspiration, new motivation. I thought of tennis, thought of the emotion that tennis provokes in me.
"It was all positives. I just felt like I had a new breath for this sport. The rest is history in terms of results. I played finals of Queen's, won Wimbledon, won Cincinnati, and won US Open. I guess we'll be hiking some more very soon."
He added: "I strongly recommend you to climb it. Some great things will happen in your life."
Well, metaphorically, Djokovic has done his fair share of climbing this season. In June, his ranking saw him fall to world No 22 - as low as he had been since 2006.
A return to world No 1 was now a real possibility. With Nadal out of action with a knee injury, Djokovic produced a flawless performance in Shanghai to win a record fourth title in convincing fashion.
After a short break, Djokovic was expected to go head to head with Nadal in Paris for the world No 1 ranking but those hopes were cut short by the Spaniard's injury withdrawal.
Back-to-back three-set victories against Marin Cilic and Federer - the latter a classic - left him fatigued in the final. In truth Karen Khachanov's level of performance was so good that Djokovic might not even have won at his physical best.
But despite the disappointment of missing out on a fifth title of the season, Djokovic knew his target of returning to the sport's Everest had been achieved.
"Reflecting on what I've been through in the last year, it's quite a phenomenal achievement," said Djokovic.
"And, of course, I'm very, very happy and proud about it. Five months ago, if you told me that, I would be - I always believe in myself, but it was highly improbable at that time considering my ranking and the way I played and felt on the court… I'll probably be able to speak more profoundly about it when the season is done and hopefully if I get to finish as No 1."
His standing at the top of the year-end rankings is now secured, following Nadal's decision to end his season and undergo surgery.
But with the ATP Finals to come and the opportunity of a sixth season-ending title, Djokovic will believe there is still one final peak to climb in his remarkable return to prominence.
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