Center court action on Day 1 included Top 20 star Sloane Stephens against Daniela Hantuchova.
Hantuchova held all 11 of her service games and broke once per set to get past Stephens, 63 75.
Over on Stadium 3, Julia Goerges slammed 10 aces en route to a 64 61 win over Bojana Jovanovski.
Two matches later on the same court, Kirsten Flipkens won by the same score against Mona Barthel.
The qualifying also wrapped up on Saturday, with former Madrid champion Aravane Rezai in action.
Rezai beat Justine Henin, Jelena Jankovic and Venus Williams en route to this title back in 2010.
Rezai led 3-0 in the third set but wound up falling to Yulia Putintseva in a thriller, 36 63 76(5).
Out on Pista 7, Bethanie Mattek-Sands and Madison Keys were playing an all-American qualies match.
Mattek-Sands was originally cruising in the match, 62 52, but wound up holding Keys off, 62 75.
The Mutua Madrid Open, held at La Caja Mágica in Madrid, is now in its fifth year as a WTA stop.
It has world class practice facilities as well - as World No.6 Angelique Kerber demonstrated.
Later on, Urszula Radwanska hit a wall named Sara Errani, falling to the World No.7, 63 61.