The Ligue 1 champions made several changes to the starting lineup having already secured qualification to the knockout stages as Group C winners, and were beaten 2-1 at the Estadio da Luz.
"We fought hard against a home side Benfica that was playing for its qualification," Rabiot told the PSG website.
"We knew it was going to be very tough. We tried to take the game to them early.
"For us, the young players, we gain a lot of experience from this type of match. To play 90 minutes here is special. The Champions League is a lot more intense that the Ligue 1."
PSG travel to Rennes in their next game on Saturday.