Novak Djokovic pulled off a hard-fought comeback victory over Ugo Humbert on his first appearance in Basel for 15 years.

Battling in the final months of the year to keep alive his chances of qualifying for the season-ending ATP Finals in Turin, Djokovic celebrated what he viewed as a "big win" by overcoming Frenchman Ugo Humbert 4-6 6-3 6-4.

The men's record 24-time major winner blasted a forehand winner down the line to end the contest after two and a half hours.

It ensured Djokovic, 11th in the race to Turin, remains in the hunt for a record 19th appearance at the ATP Finals, for which only the year's top eight performers qualify.

The 39-year-old beat great rival Roger Federer to win the Basel title in 2009, and had not played at the event since 2011.

"I was under attack from the very first point and had to weather the storm," Djokovic said.

"It's my first indoor match, so I expected to be a little bit rusty in a tough draw. It is a big win for me, I know there are quite a few things I can do better but a win is a win, and I will take that today."

This was Djokovic's 20th tour-level win of the year. It is the 21st consecutive season of his astonishing career in which he has achieved that tally.

After conceding the first set, Djokovic hung on against the 38th-ranked Humbert as he twice saved break points to escape an immediate setback in the second.

But the Serb, contesting his first indoor event since winning the Athens title last November, was solid from there, breaking Humbert's serve for the first time in the following game to kickstart his fightback.

Djokovic entered the tournament 319 points behind Spain's Rafael Jodar, who currently occupies the final ATP Finals qualification spot and also gained 50 points after coming through his first-round match.

Djokovic is also bidding to match Federer (103) for the second-most men's tour-level titles in the Open era in Basel, after ending a year-long wait for his 102nd title in Beijing in October.

Elsewhere, Great Britain's Harriet Dart progressed to the quarter-finals of the Guangzhou Open with a three-set victory over second seed Janice Tjen in China.

British number five Dart outlasted her Indonesian opponent as she prevailed 6-4 3-6 6-3 after two hours and 28 minutes.

Dart, ranked 115th in the world, will face former world number two Paula Badosa, after the Spaniard took just 67 minutes to beat Austria's Sinja Kraus 6-1 6-4.