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.