Breaking the Russian Olympic Committee athlete three times, Nishikori has now won six of his seven matches at the Olympics dating back to 2016.
Nishikori powers past Rublev in front of home country fans
As would be expected, the match was very competitive with each man taken to deuce in his opening service game, but managed to hold on. A wonderful forehand winner down the line on break point gave the 2016 Rio bronze medalist a 3-1 lead.
Rublev would rally and break back in the seventh game, but he watched as Nishikori scooped a backhand down the line to regain his break advantage and on set point, an unreturnable serve wide gave him the first set.
Each man held comfortably through their first four games of the second set until Rublev was forced to save a pair of break points to take a 3-2 lead. He wasn't as fortunate in his next service game as Nishikori broke for a 4-3 lead.
Pushed to deuce, but ultimately holding on, the former US Open finalist would serve for the match at 5-4 and on triple match point, another huge serve handcuffed Rublev and Nishikori had a famous victory.