Nadal dropped just 14 points on serve in a 6-4, 6-3 victory over Jarkko Nieminen. Nadal is 7-0 lifetime versus Nieminen. Their last previous meeting was in Monte Carlo last year in the second round.
Nadal didn't face a break point until he was up 5-2 in the second set. He lost that point but quickly posted his fourth break of the day to end the match.
Nadal, ranked No. 2 in the world, is seeking an eighth consecutive title at Monte Carlo. A win this week would give Nadal a record 20th Masters tournament championship.
World No. 1 Novak Djokovic improved to 7-0 against Andreas Seppi with a 6-1, 6-4 win Wednesday. Djokovic saved all three of the break points he faced.
Thomaz Bellucci knocked off fifth-seeded David Ferrer 6-3, 6-2 in just more than an hour. Bellucci won 70 percent of the points on serve and dropped just five points in four second-set service games.
The only other seeded player to lose Wednesday was No. 15 Jurgen Melzer, who fell to Julien Benneteau 6-4, 6-3.
No. 6-seeded Tomas Berdych got by Marin Cilic 7-6 (7-3), 6-1; seventh-seeded Janko Tipsarevic topped Albert Montanes 6-2, 6-3; and No. 8-seeded Nicolas Almagro stopped Potito Starace 7-6 (7-3), 6-1.
Only two of Wednesday's 13 matches went three sets. That includes No. 16-seeded Alexandr Dolgopolov, who beat Bernard Tomic 6-2, 5-7, 6-1 and earned a third-round shot at Djokovic. Also, qualifier Mikhail Kukushkin defeated Filippo Volandri 7-6 (10-8), 2-6, 6-2.