Olympic gold continues to elude Serbia's Novak Djokovic and his quest for the calendar "Golden Slam" is over.

With his 6-1, 3-6, 1-6 semifinal loss to Germany's Alexander Zverev on Friday, the world No. 1 Djokovic will advance to his third bronze medal match in four Olympic appearances.

Djokovic, who didn't drop a set through his first four matches of the tournament, faced his first challenge in the No. 4-seeded Zverev. Although Djokovic put up a 6-1 win in the first set, Zverev battled back to take the second set, then broke Djokovic to open the third and went up 4-0 before Djokovic finally won a game.

Djokovic will play Spain's Pablo Carreno Busta for bronze; Zverev will play the ROC's Karen Khachanov for gold.

After winning the first three Grand Slams this year, Djokovic seemingly had a strong shot at becoming the first man to win the calendar Golden Slam (all four Grand Slams plus the Olympics in one year). Many of the sport's big names, including Roger Federer and Rafael Nadal, opted out of the Olympics. 

Djokovic, 34, won the bronze medal in 2008, then lost to Juan Martin del Potro in the bronze medal match at the 2012 Games and the first round in 2016. In the quarterfinals this year, Djokovic tied the 2012 champion Federer's record of 13 Olympic match wins. 

Later on Friday, Djokovic will play in the mixed doubles quarterfinals with Nina Stojanovic, so an Olympic gold medal is not out of the question entirely.