Top seed Carlos Alcaraz survived a huge scare against Finland's Emil Ruusuvuori as his defence of the Madrid Open title began with a hard-fought comeback win.
Spain's Alcaraz, who turns 20 next week, overcame a slow start to win 2-6 6-4 6-2 against the world number 41.
There were fewer concerns for women's top seed Iga Swiatek, who won 6-3 6-2 against Austria's Julia Grabher.
However, Wimbledon champion Elena Rybakina suffered a surprise defeat to Russia's Anna Kalinskaya.
The Madrid Open is one of the most prestigious tournaments outside of the Grand Slams and an important clay-court event in the build-up to the French Open, which starts on 28 May.
Alcaraz fights back after being 'about to lose'
Alcaraz is the favourite to win the ATP Masters 1000 event with Novak Djokovic and Rafael Nadal absent because of injury.
The world number two defended the Barcelona title last week without dropping a set, but on his return to the Spanish capital initially lacked clarity and assurance in his shots.
Ruusuvuori dominated his service games in the first set, winning 100% of first service points and dropping just two on his second serve.
But the contest swung back in Alcaraz's favour after he saved five break points to stop his opponent moving 4-2 ahead in the second set.
"It was really tough, I was about to lose. He was just one point away at 3-2 in the second set - it was like a match point for him," US Open champion Alcaraz said.
"Emil was better than me until 3-3 in the second set. It was tough to come back but I finished with a lot of confidence."
Alcaraz will play Bulgaria's Grigor Dimitrov next after the 26th seed won 7-6 ( 8-6) 7-6 (7-2) against France's Gregoire Barrere in his second-round match.
Russian fifth seed Andrey Rublev moved into the last 32 with a 6-2 6-4 success against Swiss veteran Stan Wawrinka, but the struggles of Norway's Casper Ruud - seeded third - continued with a 6-3 6-4 defeat by Italian qualifier Matteo Arnaldi.
Ruud, who reached the French Open and US Open finals last year, has only won back-to-back matches at one tournament this year - when he won the Estoril title.
In the WTA event, Poland's world number one Swiatek breezed through her opening match as she extended her recent clay-court record to 23 wins from her past 24 matches on the surface.
Kazakhstan's Rybakina, seeded seventh, lifted the Indian Wells title and reached the Miami final, but has won one of her opening three matches on the European clay after being beaten 7-5 4-6 6-2 by world number 60 Kalinskaya.
American third seed Jessica Pegula reached the third round by beating Poland's Magdalena Frech, while 22-year-old American Alycia Parks shocked Belarusian two-time finalist Victoria Azarenka in a straight-set win.
Murray to play clay-court Challenger
Britain's former world number one Andy Murray has been granted a wildcard into next week's clay-court ATP Challenger event in Aix-en-Provence.
Murray, 35, lost to Italian qualifier Andrea Vavassori in the Madrid first round on Thursday and needs matches on the clay to prepare for the French Open, which starts on 28 May.
An all-British match saw Heather Watson beat Harriet Dart 3-6 6-4 6-2 to reach the semi-finals of an ITF event - the level below the main WTA Tour - in Corsica.
Source: BBC
BDST: 1416 HRS, APR 29, 2023
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