The Lions, who feature a tough, physical defense and a formidable passing attack, came to San Francisco with a chip on their shoulder, having lost to the 49ers in the now-infamous game in which 49ers coach Jim Harbaugh and Lions coach Jim Schwartz got into a post-game beef.
Schwartz took offense to Harbaugh's overly exuberant handshake and slap on the back, and the two nearly came to blows.
The 49ers led from start to finish as they held the potent Detroit offense, led by QB Matthew Stafford and wide receiver Calvin Johnson, at bay.
The win was a strong statement by the 49ers that they are a team to be reckoned with. In the first two weeks of the season, the Niners have defeated Aaron Rodgers and Stafford, two of the NFL's top quarterbacks who lead very good teams.
Let's take a deeper look at 10 of the most noteworthy developments for the 49ers in this game.