Defending champion Kei Nishikori rallied to reach the semi-finals of the $647,000 ATP US Indoor Championships on Friday but Australian third seed Lleyton Hewitt was eliminated by American Michael Russell.
Nishikori battled back to defeat Russian Alex Bogomolov 3-6, 6-3, 6-2 while Russell beat Hewitt 6-3, 7-6 (8/6), taking his first victory in four career meetings with the Aussie in one hour, 48 minutes.
Nishikori, an ATP top seed for the first time, saved all four of the break points he faced in the final set to win after two hours and 18 minutes.
"It wasn't easy," Nishikori said. "My tennis level is not quite 100 percent yet, so I hope I can get better. I have a lot of confidence and my goal is to win the tournament."
Nishikori, ranked 16th, has never before played Russell, who is ranked 98th and has never won an ATP title.
Taiwan fourth seed Lu Yen-Hsun and American Alex Kuznetsov were to meet in a later quarter-final with that winner to face either American Jack Sock or Croatia's Ivo Karlovic in the last four.
Bogomolov, rated 80 spots below Nishikori and still seeking his first ATP title at age 30, broke Nishikori's first two service games for a 4-0 lead.
Nishikori broke back in the seventh game but Bogomolov held in the ninth to take the first set.
The second set featured two early exchanges of breaks before Nishikori held for a 4-3 edge, then broke the Russian and held again to force a third set.
Nishikori, 24, broke for a 2-1 edge and again to seize command before fighting off the Russian's final break chance in the last game.
"His ranking might not be top 50 but he can play," Nishikori said.
Nishikori, who won two singles matches and shared a doubles triumph to spark Japan over Canada in Davis Cup play earlier this month, seeks his fourth career ATP crown.
His titles have come as a teen at Delray Beach in 2008, at Tokyo in 2012 and last year at Memphis when he dispatched Spain's Feliciano Lopez in the final.