Anderson suffered a side strain after taking six first-innings wickets during the third Test victory at Edgbaston which put England 2-1 up in the series with two matches to play.
“Jimmy Anderson's absence makes a huge difference,” Pietersen said.
“What he did in the first innings at Edgbaston shows why. It gives the Aussies a psychological lift. Knowing they don't have to face the skill and movement of Anderson's bowling at the start of an innings is a huge boost.
“Any batsman, coming to England, facing Jimmy on an overcast day and on a green wicket would be worried about facing him. He's world class.
“Aside from the skill and the wickets he takes, Jimmy energises the team.”
Stuart Broad will lead the England pace attack in Anderson's absence and Steven Finn, rejuvenated after taking eight wickets at Edgbaston, the fit-again Mark Wood and Ben Stokes will support him in the match which starts on Thursday.
“England's bowling is still strong,” Pietersen said.
“Steve Finn was excellent in the last Test, Stuart Broad has had an excellent series and Mark Wood has had a promising start to his test career. I like that mix of bowling.”
Pietersen, however, is concerned about the form of inexperienced opener Adam Lyth.
“Adam Lyth is finding out the difference between test cricket and county cricket,” said Pietersen, an ambassador for Paddy Power.
“It's a huge step up and you don't get as many loose deliveries as you would at county level. He needs to be busier at the crease.
“It looks like he could get out on every single ball. He's got to be positive and look to score, not to stand around and push and prod at deliveries.
“Losing one of your openers cheaply puts huge pressure on the middle order.”
Pietersen stressed the need for England to maintain a positive approach.
“England can't have any thoughts in the back of their minds about a draw being acceptable here and another draw at the Oval,” he said.
“You look to beat Australia. The players showed last week that they're comfortable with being aggressive, they need to maintain that for this week. It swings and seams a lot at Trent Bridge so they need to be confident of beating Australia there and sealing the Ashes victory.” – Reuters
Original source: England can cope without Anderson - KP