The 34-year-old joined the Packers after being released in March after a campaign in which he secured 7.5 sacks, his lowest total since 2007.
"Well, 34 is not so old. Not for some of us. There's no evidence of any decline in his play, in our opinion. He still has the same athletic traits that he had coming out," Thompson said, the Milwaukee Journal Sentinel reports.
Peppers signed a three-year deal with Green Bay and is expected to line up in various roles given his versatility in the upcoming campaign.