ATP roundup: Frances Tiafoe battles back in Stockholm
Despite Ymer winning 47 of his 59 first-service points (80 percent) and holding a 20-11 advantage in aces, Tiafoe controlled both tiebreakers. He leapt out to a 6-0 lead in the second-set tiebreaker and won it on his fifth set point before cruising in the third-set showdown as well.
Tiafoe will face Finland's Emil Ruusuvuori in the quarterfinals after Ruusuvuori swept Czech opponent Jiri Lehecka 6-2, 6-2.
Ymer's younger brother Mikael Ymer, meanwhile, took down eighth seed Tommy Paul 6-2, 6-3 and will face top seed Stefanos Tsitsipas of Greece in the next round. No. 5 seed Alex de Minaur of Australia was a 6-4, 6-2 victor over J.J Wolf.
European Open
Three seeded players bowed out during Thursday's second-round action in Antwerp, Belgium, headlined by third seed Diego Schwartzman of Argentina losing to Belgium's David Goffin 7-6 (3), 6-2.
Goffin served up six aces to Schwartzman's one and saved both break points he faced in the second set.
Sebastian Korda took down Russian fourth seed Karen Khachanov 7-5, 7-6 (9). Korda rallied back from down 6-3 in the second-set tiebreaker and saved four set points in all.
Austria's Dominic Thiem outlasted Argentina's Francisco Cerundolo, the sixth seed, 6-1, 1-6, 7-5. Second seed Felix Auger-Aliassime of Canada was spared, as he bested Frenchman Manuel Guinard 6-3, 6-3.
Tennis Napoli Cup
No. 2 seed Matteo Berrettini beat Spain's Roberto Carballes Baena and No. 4 Lorenzo Musetti defeated Serbia's Laslo Djere 7-5, 6-3 to ensure two Italians reached the quarterfinals in Naples, Italy.
Elsewhere, Mackenzie McDonald and Chinese qualifier Zhizhen Zhang each won two matches in one day to advance. McDonald beat Italian qualifier Francesco Passaro 6-3, 7-5 before surprising No. 3 seed Roberto Bautista Agut of Spain 6-4, 6-4.
Chinese qualifier Zhizhen Zhang beat Hungary's Marton Fucsovics 6-4, 7-6 (8) and outlasted No. 6 seed Sebastian Baez of Argentina 7-6 (5), 7-6 (11). Zhang saved two set points in the second-set tiebreaker against Baez before winning on his fifth match point. Zhang and McDonald will meet in the quarterfinals.
No. 5 seed Miomir Kecmanovic of Serbia, Taro Daniel of Japan and Daniel Elahi Galan also moved on to the quarters.