"When you're on a run like this, it's hard work that's needed," he told BBC Radio Solent.
"Maybe we need to get a little bit more nasty. Other teams are doing it to us and we accept things too easily."
He continued: "We need to start getting on top of other teams. We have good players but they're not coming through because we're not being nasty."
And Whittingham has some more advice for his players: "Don't accept things for what they are, get after your team-mates a little more. It's OK all getting on but sometimes you have to have some rucks to get it right."
The former Pompey and Sheffield Wednesday midfielder is preparing for Saturday's game with Doncaster, with the club unable to appoint a permanent manager until they come out of administration and are taken over by the Pompey Supporters' Trust.
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