With qualification already assured from Group C, head coach Blanc took the opportunity to rest several key players, including Zlatan Ibrahimovic and Thiago Silva.
And that decision proved costly as the Portuguese side secured a 2-1 victory at Estadio de Luz on Tuesday, although they still failed to qualify for the last 16 as Olympiacos defeated Anderlecht 3-1 and went through courtesy of their better head-to-head record over Jorge Jesus' men.
The visitors took the lead after 37 minutes when Jeremy Menez did well to keep the ball in play and cross for Edinson Cavani, who applied the finish.
However, Benfica were level shortly afterwards when Lima scored from the penalty spot.
The home fans were on their feet again close to the hour mark when Nicolas Gaitan prodded home the winner in the PSG penalty area.
And Blanc pinpointed a dip in his side's display after the break as the reason for the loss, although he remains confident that PSG can go far in the competition.
"I am disappointed with the performance of my team in the second half," he said. "It is the second half where we had a problem.
"We lacked a bit of ambition and Benfica played (well). For what they created in the second half they deserved the win.
"There has, of course, been lessons, both individually and collectively. Hopefully PSG will be able to win the Champions League but before that there will be plenty of games to play."
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