San Francisco beat Super Bowl champions Seattle 32-29 in a typically brutal contest between divisional rivals, with the Niners having defensive star Dre Greenlaw ejected early on for a headbutt on Ernest Jones, who was not wearing a helmet, on the sidelines.
Both defences are elite and forced a season-high seven turnovers in the game, with the 49ers in particular taking advantage by scoring three touchdowns from theirs. The 21 points off turnovers was the most Seattle have allowed in a decade.
Brock Purdy eventually got San Francisco over the line thanks to new wide receiver Mike Evans, who had 113 yards receiving and a touchdown, taking some great catches late on.
The only team to have a top-five scoring offence and defence, the 49ers again have injury problems this season, but if Evans stays fit he could be the missing piece in the puzzle.
San Francisco are now 5-0 for the third time under head coach Kyle Shanahan. They made the Super Bowl on both previous occasions and, if they keep finding ways to win, they have every chance again.
The Minnesota Vikings are also 5-0 after another defensive masterclass from Brian Flores' unit in their 23-13 win at the slumping New Orleans Saints.
With wins over the Saints (1-4), Tampa Bay Buccaneers (1-4) and Miami Dolphins (0-5), we will know more about the Vikings after their bye, but allowing only 13 points a game will always give you a chance.
There was a comedy of errors at the end of the Washington Commanders' 27-27 tie with the New York Giants as both teams fluffed their lines with victory within their grasp.
The Giants scored two late touchdowns to force overtime but, when within range of a winning field goal, they ran the ball with Cam Skattebo, who fumbled to lose possession.
Washington then had the game at their mercy in the dying seconds but, instead of taking the kick, ran a play - and ran out of time.
With play-calling like that, neither team deserved to win.
The Baltimore Ravens showed them both how it is done as quarterback Lamar Jackson's back-up Tyler Huntley earned a 30-23 overtime victory at the Atlanta Falcons, throwing a touchdown with 40 seconds left of regulation time before running in the game-winner in the extra period.
The Ravens are 4-1 and lurking.
More poor finishing came in the rain in New York as the Cleveland Browns missed an extra point and then Corey Bojorquez fumbled a late punt which the Jets turned into the winning touchdown.
Although it was messy at times, the Jets seem to have a fine defence, with eight sacks on Deshaun Watson in their 17-12 success.