British number one Kyle Edmund exited the Millennium Estoril Open in Portugal with a 6-3 1-6 6-0 quarter-final defeat against Joao Sousa.
After a disappointing start in the opening set, Edmund clawed his way back into contention by overwhelming his Portuguese opponent in the second set.
But Edmund, who was third seed in the clay-court tournament, was defeated in the decider.
Stefanos Tsitsipas fought back from 3-0 down in a final-set tiebreak to knock out defending champion Roberto Carballes Baena 6-7 (2/7) 6-2 7-6 (7/3).
The Greek's two-hour and 37-minute success set up a semi-final clash with home favourite Joao Sousa, who overcame third seed Kyle Edmund 6-3 1-6 6-0.
Malek Jaziri is within touching distance of his first ATP World Tour final at the TEB BNP Paribas Istanbul Open after beating Jiri Vesely 3-6 6-4 6-1.
The 34-year-old Tunisian, who knocked out top seed and defending champion Marin Cilic in the second round, will play Laslo Djere of Serbia after he beat fifth-seeded Italian Paolo Lorenzi 6-7 (5/7) 7-5 7-6 (7/3).
France's Jeremy Chardy defeated Thomas Fabbiano 6-2 6-2 and will play in the other semi-final against Taro Daniel, who fought back from 4-0 down in the deciding set to beat Rogerio Dutra Silva 1-6 6-1 6-4.
Top seed and defending champion Alexander Zverev is back in the semi-finals of the BMW Open.
The world number three overcame fellow German Jan-Lennard Struff 6-3 6-2 in 62 minutes, wrapping up the match with an ace on his second serve.
Zverev set up a mouth-watering clash against fourth seed Hyeon Chung in the last four.
Two of the ATP World Tour's most exciting young players will go head to head after Chung advanced with a 6-3 6-4 victory over Slovakian qualifier and 2014 champion Martin Klizan.
The other semi-final in Munich will see Philipp Kohlschreiber face Maximilian Marterer.
Home favourite and three-time champion Kohlschreiber battled past number two seed Roberto Bautista Agut 6-4 6-4 while Marterer defeated Hungarian Marton Fucsovics 6-3 6-4.