Nadal, who lost in the final at Monte Carlo to Novak Djokovic, said, "right now, I think things are going well." The world No 5 has reached five consecutive finals since returning in February from a knee injury and said "after everything that has happened, simply to be competing in these tournaments makes me happy."
Russian qualifier Dmitry Tursunov stunned the crowd by defeating four-time runner-up David Ferrer in three sets.
Ferrer, who was top-seeded here for the first time in his career, crashed out 7-5, 3-6, 6-1.
Ferrer said he "did not feel well on the court today."
Results from the third day of the $795 000 WTA Stuttgart tournament on Wednesday (x denotes seeding):First round
Dmitry Tursunov (RUS) bt David Ferrer (ESP x1) 7-5, 3-6, 6-1
Martin Klizan (SVK x11) bt Albert Montanes (ESP) 6-3, 6-4
Juan Monaco (ARG x7) bt Bernard Tomic (AUS) 6-0, 6-2
Milos Raonic (CAN x5) bt Edouard Roger-Vasselin (FRA) 6-4, 6-2
Tommy Robredo (ESP) bt Grigor Dimitrov (BUL x14) 7-5, 6-1
Marcel Granollers (ESP x15) bt Blaz Kavcic (SLO)
Rafael Nadal (ESP x2) bt Carlos Berlocq (ARG) 6-4, 6-2
Nicolas Almagro (ESP x4) bt Ivan Dodig (CRO) 6-1, 7-5
Albert Ramos (ESP) bt Jerzy Janowicz (POL x9) 4-6, 6-2, 6-3
Benot Paire (FRA x13) bt Pablo Andjar (ESP) 6-4, 5-7, 6-3