Three-time Grand Slam champion Stan Wawrinka, steadily rebuilding his career after undergoing two knee operations, reached his first semi-final since last year's Roland Garros when he downed Serbia's Viktor Troicki 6-1, 7-6 (7/3) at the Sofia Open on Friday.
Top seed Wawrinka took his record over sixth-seeded Troicki to 9-0 as he stayed on course for what would be a 17th tour-level title.
"I think my level is getting better," 32-year-old Wawrinka told atpworldtour.com. "I'm serving and moving better and it's a great win for me."
Wawrinka next faces Bosnian qualifier Mirza Basic for a place in Sunday's final.
"I'm doing everything to keep winning, that's for sure," added Wawrinka after just his third win of 2018.
"I'm enjoying my time, I'm fighting on the court and that's the most important."