The black, green and gold go into derby day on the back of a 63-13 drubbing at the hands of Saracens last Saturday.
Saints lost the second half 48-0 as they suffered a fourth huge defeat in as many games against Saracens this season.
And they will face another massive task on Saturday as they face a reinvigorated Tigers team who have won their past five matches.
"You can't ask for a bigger game," said Dickens, who has seen his side lose their past five games.
"The players need to regroup, as do the coaches, and we need to go up there with a positive attitude.
"We need to fight for everything.
"We can't afford to just play for 40 minutes like we did on Saturday."