Pompey extended their winless run to 14 games after first half goals from Febian Brandy and Will Grigg gave Walsall their fourth win in five games on Friday night.
Dean Smith's men had previously gone 16 without a win and Whittingham is hoping to use the Saddlers' upturn in fortunes as inspiration for his struggling side.
He said: "Walsall were on a similar run to us and now they have won four out of five, but we need to find almost promotion form.
"Until they scored there was not much in it, but the first goal gave them a lift. It's not funny being on a losing run, but we have to make sure we are doing the right things and take all the positives we can.
"We always knew it was going to be a battle in the situation we are in, but our fans applauded the players off at the end.
"We lost two goals through silly defensive decisions tonight. We are facing a big task, but you never know.
"We now need to sort out which players are going to be with us for the rest of the season, and try to bring a couple in."