Former Rolex Paris Masters champion Rune struggled on second serve. Rune won just eight of 25 second-serve points and faced 14 break points in the match.
“I’m very excited, I’m happy with my performance today,” Uchiyama said. “I couldn’t imagine winning in two sets, I was just thinking about my performance, I had to play 100 per cent the whole match to get the chance to beat him, so it went well for me today.”
The 32-year-old Uchiyama advanced to his third career Tour-level quarterfinal where he will face former US Open champion Marin Cilic.
Wild card Cilic cracked 15 aces, won 26 of 28 first-serve points and faced just one break point powering past Yoshihito Nishioka 6-4, 6-1 in 69 minutes.
Spaniard Roberto Carballes Baena saved two of three break points rallying past American lucky loser Mitchell Krueger 3-6, 6-3, 6-4.
