Defending champion Carlos Alcaraz reached his seventh semi-final of the year on Friday with a straight-sets win over Facundo Bagnis at the Umag clay-court tournament.
The 19-year-old Spaniard raced away with the first eight games of the match before sealing a 6-0, 6-4 win over his 120th-ranked opponent from Argentina.
Having started the week at a career-high of five in the world, Alcaraz will replace Stefanos Tsitsipas at number four should he defeat Italian qualifier Giulio Zeppieri in Saturday's semi-finals.
"It means a lot to be able to reach the number four ranking, to have a chance to do it," Alcaraz said after Friday's match.
"It's amazing for me. I think I'm playing really well. I feel really comfortable playing here, a lot of confidence right now."
Zeppieri defeated Spain's Bernabe Zapata Miralles 7-5, 6-4 to make the last four.
Meanwhile, second seed and world number 10 Jannik Sinner reached his first semi-final of 2022 by seeing off Roberto Carballes Baena 6-4, 7-6 (7/5).
"I've won many matches, but I think I've had some unfortunate moments this year," said Italy's Sinner after his win over 86th-ranked Carballes Baena of Spain.
"But here I am, the first semi-final of the year, and hopefully I can show some good tennis also in the next round."
The 20-year-old will face 136th-ranked compatriot Franco Agamenone for a place in the final.
Unseeded Agamenone made the last four by beating 2018 champion Marco Cecchinato, also of Italy, 6-2, 6-1.