The Scot marked his 21st birthday by going down 6-3 6-2 to the Spaniard who was simply too good, despite Murray showing glimpses of the form that saw him dispatch Dmitry Tursunov and Gilles Simon earlier this week.
Murray told BBC Radio Five Live: "I just want to concentrate right now on getting closer to the guys at the top. Whether or not I'll play as well on clay as on other surfaces, I don't really know."
He added: "But my game is definitely getting better and that is one positive thing I can leave with."
Murray began strongly by holding serve to love in the opening game, but an horrific smash into the net set the tone for his next attempt as Nadal gratefully accepted the first of two break points.
The British number one saved a first set point on his serve in the ninth game, but two weak forehands into the net offered second and third chances to Nadal - the latter converted when the birthday boy volleyed long to concede the first set 6-3.
Murray immediately hit back, however, to claim a first break in the opening game of the second set, but Nadal instantly got back on terms to reassert his superiority.
Nadal clinched a second break in the fourth game, sealed with a looping forehand up the line which brushed the chalk, to move into an ominous 3-1 lead.
The Spaniard had a first match point on Murray's serve in the eighth, and although that was saved, another forehand into the net put an end to the Briton's preparations for Roland Garros.
Murray told BBC Sport afterwards: "Nadal's forehand is the best shot in tennis. When you go behind against him on clay it's very hard to get back."