Novak Djokovic described his return to the world number one ranking as a "phenomenal achievement" on Thursday as he coasted into the Paris Masters quarterfinals.
Four-time Paris champion Djokovic made the last-eight when Bosnian opponent Damir Dzumhur retired injured trailing 6-1, 2-1.
Djokovic will replace Rafael Nadal as the world's top player on Monday after a two-year absence.
The 31-year-old's elevation is remarkable as it comes just five months after he slumped to 22 in the world -- his lowest ranking for 12 years -- when he was knocked out of the French Open in the quarter-finals.
Since then, however, he has won Wimbledon and the US Open, taking his Grand Slam tally to 14, winning 20 consecutive tour-level matches for the sixth time, and 29 of his past 30 encounters.
"Reflecting on what I've been through in the last year, it's quite a phenomenal achievement," said Djokovic who will face Marin Cilic for a spot in the semifinals.
"I'm very, very happy and proud about it. Five months ago, it was highly improbable 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."
"It's not the end of the season. Rafa obviously is struggling with injuries since the US Open. But the race is still there," added Djokovic after extending his sequence of consecutive winning sets to 30, passing his previous best mark of 29 from 2015.
"Roger is in the race. Rafa is in the race. It depends who is going to play the ATP Finals in London. So as I said, I can't be too ecstatic about it."