Damir Dzumhur upset fourth seed Matteo Arnaldi 7-6(5), 6-7(4), 7-6(4) in three hours and 42 minutes to reach the semi-finals at the Plava Laguna Croatia Open Umag Thursday evening.

In a match decided by the finest of margins, Arnaldi served for the opening set twice before Dzumhur snatched it in a tie-break. In the second, the 34-year-old stood just two points from victory at 5-3, 30/30, but Arnaldi dug deep to force a decider by winning the second-set tie-break. Ultimately, Dzumhur held his nerve to edge the third-set tie-break and complete a hard-fought victory.

"Matches like these, this is why we love the sport," Dzumhur, the 2025 semi-finalist, said. "It was maybe too long, but I think it was a great fight from both. And I want to thank Matteo for sharing the court with me. It was an amazing match."

The 34-year-old finished having saved 8 of the 11 break points he faced, according to Infosys ATP Stats. With the victory, Dzumhur advanced to his first tour-level semi-final of the season, in which he will face Alex Molcan. Molcan rallied to upset second seed Alejandro Davidovich Fokina 3-6, 6-1, 6-2 in the final match of the day.

Roman Andres Burruchaga’s Umag run continued Thursday, when the Argentine defeated seventh seed Camilo Ugo Carabelli to advance to the semi-finals at the clay-court ATP 250 event. The No. 67 player in the PIF ATP Rankings, Burruchaga backed up his second-round win against top seed Flavio Cobolli with a hard-fought 6-2, 2-6, 6-3 victory against good friend and countryman Ugo Carabelli.

"I am so happy with the win and for reaching the semi-finals," Burruchaga said. "Sadly, Camilo is a very good friend and also a very good competitor. I have played wth him many times. It is always a good fight with him. We both fought until the end [today], but fortunately it was a win for me."

Watch highlights from Burruchaga vs. Ugo Carabelli QF clash:

With the triumph, Burruchaga improved to 2-0 in the pair's Lexus ATP Head2Head series. The next test for Burruchaga in Umag will be a semi-final meeting with 21-year-old Daniel Merida.

In the opening match of the day, Merida produced a composed performance to sink Titouan Droguet 6-1, 6-3 in 64 minutes to reach his second tour-level semi-final of the season. Following his victory, the Spaniard jumped 10 spots to No. 72 in the PIF ATP Live Rankings and is guaranteed a career high when the rankings are released on Monday.