Champions Carlos Alcaraz and Aryna Sabalenka through in Madrid Open
Alcaraz returned after a month out to begin his double defence with a convincing 6-2, 6-1 win over Alexander Shevchenko, while Sabalenka survived a tense three-set tussle against the in-form Magda Linette.
Men's world number three Alcaraz shone on home clay after a forearm problem led to his withdrawals from the Monte Carlo Masters and Barcelona Open.
"It's been quite a tough month for me, with the uncertainty over when I'd be back," said Alcaraz.
"The priority today was to see how I felt, in a difficult match.
"The feelings were very good, and I think I played at a very good level despite coming without rhythm... I am very happy and it's a pleasure to play here in Madrid again."
Wearing a protective sleeve on his right arm, two-time Grand Slam winner Alcaraz quickly dispelled any doubts after his time out by flying out of the blocks in the first set with a break.
The Spaniard was as exciting as ever, frequently on the attack, and secured a second break in the fifth game for a 4-1 lead.
Indian Wells winner Alcaraz hit the net with a drop shot to let the Kazakhstani back in but broke again himself for a 5-2 advantage which he served out.
Alcaraz pulled off two second set breaks for a 3-0 lead but again allowed his 23-year-old opponent to cut the deficit before striking back with a third break, which he consolidated for 5-1.
The 2022 and 2023 Madrid winner and second seed wrapped up his victory in little over an hour with another break when Shevchenko sent a forehand long.
Alcaraz will face Thiago Seyboth Wild in the third round after the Brazilian surprised Lorenzo Musetti 6-4, 6-4.
Andrey Rublev ended a four-match losing streak with a straightforward 6-1, 6-4 win over Facundo Bagnis.
"It feels really great after a while to start with a win and I'm happy with my performance," said Rublev, who lost his temper and obliterated his racquet after a first-round exit in Barcelona.
Poland's Hubert Hurkacz hit nine aces as he powered past Briton Jack Draper 6-1, 7-5.
'Didn't handle my emotions'
In the women's draw, Sabalenka edged the wily Linette 6-4, 3-6, 6-3.
The Australian Open winner has struggled since her triumph in Melbourne and her Polish opponent fought well in the two-hour nine-minute contest.
Big-hitter Sabalenka, ranked second in the world, edged the first set but struggled in the second as Linette broke to love and then consolidated for a 4-1 lead.
The 32-year-old then carved out three break points in the sixth game but although she could not take them, eventually steered the match to a deciding third set.
Two-time Grand Slam champion Sabalenka saved three break points to stay on serve and then found a net cord winner to break herself for a 5-3 lead.
Sabalenka wrapped up her narrow victory over the world number 48 by smashing down an ace and will face Robin Montgomery in the third round after she upset Katie Boulter 1-6, 6-3, 6-4.
"I think in that second set she just put a little extra pressure on my serve, and I just didn't handle my emotions well," said Sabalenka.
"We went to a third set, and I'm just happy that I was able to close this match with a win."
Elena Rybakina eased past Lucia Bronzetti 6-4, 6-3.
The Kazakhstani, ranked fourth in the world and with a tour-leading three titles this season, continued her good form after triumphing in Stuttgart last week.
Rybakina faces Egyptian Mayar Sherif in the next round after she surprised Stuttgart runner-up Marta Kostyuk 6-2, 7-5.
Chinese fifth seed Zheng Qinwen retired with a thigh injury from her match against Yulia Putintseva, who had taken a 7-5, 2-0 lead.