A first-half Lionel Messi hat-trick had the Catalans three goals to the good by the 41st minute at the Mestalla on Sunday.
However, Valencia striker Helder Postiga struck a three-minute brace in the shadows of half-time to give the hosts hope of a stirring comeback.
But the La Liga champions held firm in the second half to post their third win from as many league matches this season, but Martino still said the creation of their healthy buffer was some of their best football so far.
"That sometimes happens in football ... one bad minute at the end of the first half. This is a difficult away game," Martino said.
"This has been the best Barca this season, because of the stadium where we played, the opponent we faced, and the way we played."
Martino admitted his champion side eased off once Messi put them comfortably ahead, courtesy of two assists from Cesc Fabregas and another from Brazilian starlet Neymar.
"What worries me most is that we gave Valencia the chance to get back into the game, we relaxed when we were three goals up," he said.
Messi completed his hat-trick after Neymar squared a low pass for the Argentine to tuck home, and Martino said his decision to play the pair together was vindicated.
"Yesterday there were doubts about the Messi-Neymar connection after their first game together. Things have been solved in 24 hours," the coach said.
Each of Javier Mascherano and Sergio Busquets played out the 90 minutes on Sunday, but Martino said the pair were both in doubt for their hosting of Sevilla on Saturday week.
"Mascherano got a serious knock on his ear. Busquets could be worse, thigh muscle tear," he said.
