Jose Maria Callejon scored the opener before Duvan Zapata's stunning strike secured the three points at the Stade Velodrome.
"I am satisfied because we won, but it seems easy for me to choose a player like Dries Mertens when he works so hard in training," Benitez told Sky Sport Italia after the 2-1 victory.
"We're at 75 per cent now. The players sacrificed themselves and worked hard all over the pitch. We know that when we work all together, we can achieve something.
"My staff worked well to analyse the opposition and everyone knew the tactical plan. I think that is the key, as if you prepare it on the whiteboard and the players follow those instructions, they know where to be and what to do."
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