Third seed Taylor Fritz reached the Rakuten Japan Open quarterfinals after being pushed to three sets by unheralded Japanese opponent Hiroki Moriya in an unexpectedly tough second-round battle on Thursday.
World No. 261 Moriya, who entered the main draw as lucky loser, bounced back from a lopsided opening set to stun the 11th-ranked American in the second, eventually going down 6-1, 3-6, 6-4 in just under two hours.
The 31-year-old journeyman was left flying the flag for the host country at Ariake Tennis Park following qualifier Rio Noguchi's 6-3, 6-1 loss to Canadian seventh seed Denis Shapovalov earlier in the day.
The 24-year-old Fritz is the highest seed left in the tournament following the surprise first-round exit of top seed Casper Ruud and the withdrawal of No. 2 Cameron Norrie. He will face fifth-seeded Australian Nick Kyrgios in the quarterfinals.
Wimbledon finalist Kyrgios earlier overcame a shaky start to secure a 3-6, 6-2, 6-2 victory against Poland's Kamil Majchrzak under the closed roof at Ariake Coliseum.