Western and Southern Open: Johanna Konta & Novak Djokovic in semi-finals
The 29-year-old has still not dropped serve all week after a 6-4 6-3 victory over the Greek player, who beat Serena Williams in the last round.
Konta dominated the one-sided match, converting three of 12 break points in a routine win over the 13th seed.
The eighth seed meets Victoria Azarenka in Thursday's semi-final (17:30 BST).
"I was really pleased I was able to adapt well and stay tough when I needed to," said Konta, whose partnership with new coach Thomas Hogstedt has started well in New York.
"I was able to compete in the parts of the match where I thought it was important for momentum."
Konta is hoping the appointment of Hogstedt, who previously coached Maria Sharapova, can help her make the leap from three-time Grand Slam semi-finalist to major champion at next week's US Open.
The Grand Slam starts on Monday at Flushing Meadows, which is also hosting the Western and Southern Open this week.
The event is usually held in Cincinnati but was moved to create a two-tournament safety bubble that also incorporates the first major since the sport was put on hold by the coronavirus pandemic.
Two-time Grand Slam champion Azarenka, 31, earned her place in the semi-finals with a 7-6 6-2 win against Tunisia's Ons Jabeur.
Japanese fourth seed Naomi Osaka reached her first Western and Southern Open semi-final after fighting back to beat Estonian 12th seed Anett Kontaveit.
Osaka, 22, trailed a set and a break before reeling off nine games in a row to turn the match in her favour.
The 2018 US Open champion will play Belgian 14th seed Elise Mertens, who needed little over an hour to breeze past American qualifier Jessica Pegula 6-1 6-3.
Djokovic extends unbeaten 2020 record
World number one Novak Djokovic extended his unbeaten record in 2020 to 21 matches as he outclassed Germany's Jan-Lennard Struff.
The 33-year-old Serb, a 17-time major champion, was in imperious form as he won 6-3 6-1 against 34th-ranked Struff.
The only blip saw Djokovic unable to serve out a second-set bagel, but he hit straight back to win in 62 minutes.
Djokovic faces Spain's Roberto Bautista Agut in Thursday's semi-finals.
"I'm very pleased overall. Until that last game I served very well, I was comfortably hitting the spots and getting free points there," said reigning Wimbledon and Australian Open champion Djokovic.
Novak Djokovic celebrates winning at the Western and Southern Open
Djokovic is looking to win his 18th Grand Slam title when the US Open starts next week
Eighth seed Bautista Agut, 32, fought back from a set and a break down to knock out Russia's defending champion Daniil Medvedev.
Medvedev, seeded third, was outstanding in a one-sided first set before Bautista Agut showed his resilience and quality to win 1-6 6-4 6-3.
"Roberto is consistent and doesn't make many errors, he doesn't drop his level," added Djokovic, who beat Bautista Agut in last year's Wimbledon semi-finals.
"He is probably the most under-rated player in the last five years and deserves more respect than he gets."
There will be British representation in the men's doubles final after Jamie Murray and Neal Skupski teed up a semi-final against Joe Salisbury and his American playing partner Rajeev Ram.
Murray and Skupski beat Germany's reigning French Open champions Kevin Krawietz and Andreas Mies in their quarter-final, while Salisbury and Ram knocked out Argentina's Horacio Zeballos and Spain's Marcel Granollers.