The Spanish boss decided to make his team selection based on freshness rather than quality, leaving Steven Gerrard, Fernando Torres and Ryan Babel on the bench.
Instead, Yossi Benayoun, Jermaine Pernnant, Peter Crouch and Andriy Voronin were given their chance ot prove themselves.
Dirk Kuyt was left out of the squad entirely, in favour of a rest ahead of the midweek Champions League clash with Porto.
Despite a promising start, Liverpool struggled to test David James in the Portsmmouth goal.
A low strike by Benayoun and an overhit pass from Voronin to Pennant in the area were the two clear chances of the first half, as the Reds lost their way slightly and allowed Portsmouth more possession.
The home side coud have quite easily taken the lead after Alvaro Arbeloa pulled Kanu's shirt in the area and referee Mike Riley awarded a penalty. Fortunately penalty hero Pepe Reina was able to save to his right.
There were even less chances in the second half, despite the arrival of Gerrard, Torres and Babel. James didn't have a saveto make in the second 45 and Portsmouth appeared happy to hold out for the point.
As the final whistle was blown Benitez must surely regret not fielding a stronger side in a game which, if won, would have seen them remain clear at the top of the Premiership.
"In the first half we were better than them," he said after the game. "That means the players were doing a good job.
"I think we played well. We played a good counter-attack. I think they had one or two clear chances from mistakes and I cannot complain about the penalty."