The Russian put up a stiff fight against the Spaniard but fell to him 7-6 (4), 7-6 (4), 6-3.
Nadal needed three minutes short of 3 hours to defeat 93rd-ranked Gabashvili on Tuesday, Aug 31.
"I prefer to play 1 hour 10 minutes. Win easier, no?" Nadal said after his match.
"But no, one match is easy, especially in a big tournament. The pressure's there. You play against players that don't have much to lose, so they play aggressive. This is difficult to stop," he added.
In the second round, the world number one will be facing Denis Istomin of Uzbekistan, who defeated Maximo Gonzalez 7-5, 7-5, 6-1 in the opening round.