The Greek second seed Stefanos Tsitsipas outmaneuvered Chilean qualifier Cristian Garin on Monday to reach the fourth round of the Miami Open, winning 6-3, 4-6, 6-4 while Elena Rybakina further strengthened her pursuit of the rare "Sunshine Double" with a win over Elise Mertens.
Tsitsipas, still dealing with an ongoing shoulder issue and playing his first match of the Miami fortnight following a bye and walkover, respectively, in the opening two rounds, had 12 aces and saved three of four break points in the two-hour match.
"I was waiting for a very long time to get out there and play," said Tsitsipas. "It almost felt like a vacation this last week, staying in Miami, so I am glad I got started.
"I won't lie, it was difficult out there against an opponent that has shown good tennis against top players in the past."
The match remained on serve until Tsitsipas broke for a 5-3 lead in the opening frame before going on to hold at love to grab the first set without facing a break point.
Tsitsipas was tested early in the second set when he fell behind 0-40 and needed to win five consecutive points to hold serve and draw level at 1-1 but could not repeat that escape at 4-5 as Garin broke to love to force a decider.
The Greek squandered two break point chances in the opening game of a third set but got the break he would need at 4-4 when Garin double-faulted while at 40-30 in a game the Chilean went on to lose before Tsitsipas served out the match.
Up next for Tsitsipas will be Russian 14th seed Karen Khachanov, who reached the round of 16 with a 6-2 6-4 win over Czech Jiri Lehecka.
Tsitsipas has a 6-0 record in head-to-head meetings against Khachanov with their most recent coming at the Australian Open semi-finals in January where the Greek prevailed in four sets to reach his first Melbourne final.
In other men's action, Argentine Francisco Cerundolo stunned fifth seed Felix Auger-Aliassime 6-2 7-5 to avenge his third-round loss to the Canadian two weeks ago at Indian Wells.
Rybakina, the 10th seed, came back from a break down to grab the first set against Mertens.
She then ramped up the pressure as she went up an early break in the second and never looked back as the Wimbledon champion moved into the quarter-finals with a 6-4 6-3 win.
Mertens, who took down a pair of seeded players in Daria Kasatkina and Petra Martic en route to the last 16, led 4-3 in the first set but Rybakina took the next six games stretching into the second frame to grab control.
If Rybakina lifts the title in Miami, she would become only the fifth woman to win the Indian Wells and Miami tournaments back-to-back, a feat known as the "Sunshine Double" given the tournaments' locations in California and Florida.
Third seed Jessica Pegula beat Poland's Magda Linette 6-1 7-5 in a match where she broke four times during a 28-minute first set and then erased a 5-2 double-break to avoid being pushed into a decider.
Pegula, a Miami semi-finalist last year who lives about 30 minutes from the tournament venue, has not dropped a set over her first three matches and will next face Russia's Anastasia Potapova, a 6-4 7-6(4) winner over China's Qinwen Zheng.
In other action, Italian 25th seed Martina Trevisan enjoyed a 6-3 6-3 win over former French Open champion Jelena Ostapenko, the Latvian 24th seed, to reach the quarter-finals of a WTA 1000 event for the first time in her career.