Djokovic overcomes illness to reach Final 4

London — Novak Djokovic overcame an illness — and Alexander Zverev — to advance to the last four of the ATP Finals.

Despite requiring a tissue to blow his nose between points, Djokovic beat Zverev 6-4, 6-1 on Wednesday to earn a second straight victory at the season-ending tournament.

“Unfortunately today hasn’t been great in terms of that (illness),” Djokovic said. “Somehow I managed to gather the strength when I needed it.”

Djokovic’s passage to an eighth semifinal at the tournament was confirmed when Marin Cilic defeated John Isner 6-7 (2), 6-3 6-4 in the late match.

The five-time champion from Serbia saved two break points at 4-4 in the opening set and then broke Zverev in the following game to take the lead. Zverev won only one more game.

“Maybe he was a little bit sick or something like that,” Zverev said. “But he still played like he felt at his absolute best. That’s kind of all that matters.”

With Zverev having defeated Cilic in the opening match of the round-robin, all three players still have a chance of reaching the semifinals.

Victory in London would cap a remarkable season for Djokovic, who has already secured the year-end No. 1 ranking after dropping as low as 22nd in June.

The 31-year-old ended a two-year Grand Slam title drought by winning Wimbledon in July before collecting his 14th major trophy at the U.S. Open two months later.