Jahvid Best

Jahvid Best is coming off his first 100-yard rushing game since the Detroit Lions drafted him 30th overall in 2010.

If he repeats that effort Sunday, he'll end the 49ers' streak of 27 consecutive games of not allowing a 100-yard rusher. The 5-0 Lions beat the Chicago Bears 24-17 Monday night as Best ran for 163 yards, including an 88-yard touchdown run that was the second-longest in franchise history.

"Any time he gets to the open field, he's capable of hitting a home run, as I'm sure you saw Monday night," 49ers defensive coordinator Vic Fangio said Thursday. "He's a big challenge for us, and he's a big part of their offense."

So is wide receiver Calvin Johnson, who's produced an NFL-record nine touchdown catches through five games.

"If defenses devote too much attention to Calvin Johnson, a guy like Best can make 'em pay," Lions coach Jim Schwartz said.

"If we can be physical and stop the run, there's a good chance we win," 49ers safety Donte Whitner said. "A lot of teams try to run downhill and test your manhood. We pride ourselves on stopping the run."

The 49ers have allowed the fewest Adjusted FP to RBs this season, so Best will not find as much room to run as he saw against the Bears. The Lions will keep him involved in the passing game, however.