Tokyo - David Goffin of Belgium advanced to the Japan Open quarter-finals after squeezing by Canada's Denis Shapovalov 7-6(7/5), 7-6(7/2) on Thursday.
Both men kept all of their service games - with Shapovalov nailing 10 aces against third-seed Goffin's four - in the close match that lasted nearly two hours.
Goffin, winner here in 2017, used his footwork to survive two break points while the big-serving Canadian kept up the pressure.
Goffin will now face either sixth-seed Marin Cilic of Croatia or South Korea's Chung Hyeon.
"It was tough. We were both really solid on our service games," Goffin said.
"But he (Shapovalov) was serving so well. A lefty, serving everywhere. Great second serves as well. So it was tough to break him today. So I had to fight."
Match data, however, provided proof that Goffin kept an edge above his opponent, landing 70 percent of his first serves, against 52 percent by Shapovalov.
In the rest of the tournament, Japanese wild card Taro Daniel defeated Australian rival Jordan Thompson 6-4, 7-6(7/3).
He will next face Australian qualifier John Millman, who defeated South African Lloyd Harris 6-3, 6-2.
World No 1 Novak Djokovic, returning from a shoulder injury, is scheduled to play French fifth-seed Lucas Pouille on Friday.