World number one Novak Djokovic is desperate to rebound after his men's singles semi-final defeat, targeting "at least one medal" for Serbia with two bronze medal matches on Saturday.

Djokovic, chasing an elusive Golden Grand Slam, went down in three sets to German fourth seed Alexander Zverev on Friday in the men's singles.

The Serbian will instead face Pablo Carreno Busta in the men's singles bronze medal match on Saturday, while he has another medal hope in the mixed doubles.

Djokovic has partnered with Nina Stojanovic and will face Australian duo Ashleigh Barty and John Peers in the bronze medal match also on Saturday.

“I feel terrible right now in every sense but tomorrow hopefully a fresh start I can recover and win at least one medal for my country,” Djokovic said.

After losing to Zverev 1-6 6-3 6-1, Djokovic's tough day was compounded with defeat alongside Stojanovic in the mixed doubles' semi-finals to the Russian Olympic Committee's Elena Vesnina and Aslan Karatsev 7-6 (7-4) 7-5.

“Tough day, a really tough day," Djokovic said. "I feel so terrible right now. I was leading by a set then a break and [Zverev] managed to turn the match around.

"He served huge, was attacking, and I was not getting any free points on my first serves.

“I've got to give him credit for turning the match around. He served extremely well. I mean I was not getting too many looks on the second serve.

"My serve just drastically dropped. I didn’t get any free points from 3-2 up in the second. My game fell apart.

“To play someone of his quality, of his level, it's just too tough to win a match [like that]. It’s just sport. He played better.”