Willis and Peterson are the favorite to be the NFL's defensive and offensive rookies of the year based on the first 12 games of the season. Willis and the San Francisco 49ers and Peterson's Minnesota Vikings meet on Sunday.
The 49ers' rush defense, coming off a rough game, will have a major challenge against Peterson, who has rushed for 1,197 yards and 10 touchdowns as a rookie.
"Our goal every week is to hold them to under 100 yards and stop whoever we're playing," Willis said. "That's our goal every week with everybody. We need a good week of preparation."
Willis recorded 18 tackles for the second consecutive game last week in a 31-14 loss to the Carolina Panthers. Those tackles felt a bit empty for Willis, who had an identical stat line the previous game in a 37-31 overtime win against the Arizona Cardinals.
"Getting 18 tackles doesn't feel like anything," Willis said. "After losing, those stats don't mean as much."
The 49ers were unable to maintain any momentum their rousing victory over the Cardinals.
The 49ers have lost nine of their past 10 games and are assured a franchise-worst fifth consecutive losing season.
The sentiment around the 49ers is that coach Mike Nolan will get a fourth season to turn things around. Despite owning a 14-31 record in three seasons, Nolan has instituted a franchise structure that appears to have the approval of owner John York.
The 49ers (3-9) have fallen out of contention in the NFC West, as they were mathematically eliminated with their loss to the Panthers. The 49ers trail the division-leading Seattle Seahawks by five games with four to play.
After jumping out to a 2-0 record and elevating their hopes for the season, the 49ers have been one of the worst teams in the NFL. That slide has come as a shock to several free agents who came to the organization expecting big things.
"This really is shocking to me," said safety Michael Lewis, who signed with the 49ers as a free agent from the Philadelphia Eagles. "I really studied this team. Then we got off to a good start but we've really faltered. I feel we have the team in place, but we just have to get better overall."
Running back Frank Gore, one week after gaining 214 total yards and two touchdowns against the Cardinals, was held to 58 yards rushing on 12 carries and 53 yards receiving on five catches.
He, like a lot of players in the locker room, is a firm believer in Nolan.
"Coach Nolan, I know he much he wants it," Gore said. "I want it for him. Coach Nolan is a hard worker. We'll get there. We just need to keep working and keep focused."