Rafael Nadal began his bid for a fifth Madrid Open title with a straight-sets win over Andrey Kuznetsov.
The Spanish fifth seed needed just an hour and 19 minutes to see off Russia's Kuznetsov 6-3 6-3.
Nadal hit 22 winners and committed just nine unforced errors while breaking serve three times in a comfortable victory.
He will face Sam Querrey or qualifier Lucas Pouille in the third round.
Andy Murray battled past veteran Radek Stepanek in three sets to get his defence of the Madrid Open off to a winning start.
The world number two made hard work of beating the 37-year-old from the Czech Republic, dropping the second set before eventually sealing a 7-6 (7/3) 3-6 6-1 victory.
Juan Martin del Potro was overcome with emotion after beating 14th seed Dominic Thiem.
The Argentine, back in action after almost a year of injury misery, ran out a 7-6 (7-5) 6-3 winner in an hour and three-quarters.
"I have just played my best match since I came back to tennis after my surgeries," he told ATPworldtour.com.
"I've had a great test against a very high-level player."
Del Potro will face American Jack Sock, who edged out Frenchman Benoit Paire in three sets.
Milos Raonic of Canada and France's Richard Gasquet also advanced into the third round while there were further wins for Gael Monfils, Nick Kyrgios, Roberto Bautista-Agut, Fabio Fognini, Pablo Cuevas, Denis Kudla, Pablo Carreno-Busta, Albert Ramos-Vinolas and Borna Coric.
In the women's tournament sixth seed Simona Halep was a comfortable winner over Italy's Karin Knapp, the Romanian registering a 6-1 6-1 triumph.
Timea Bacsinszky, Laura Siegemund, Carla Suarez Navarro and Dominika Cibulkova are also through along with Samantha Stosur and Anastasia Pavlyuchenkova, who received walkovers.