The San Francisco 49ers stretched their winning streak to six games and clinched the NFC West with a 45-29 win over the Arizona Cardinals.San Francisco quarterback Brock Purdy improved upon his MVP credentials with four touchdowns and 242 passing yards in another stellar addition to his breakout season.Arizona put some pressure on early with a touchdown in the first two minutes, but the 49ers responded with back-to-back touchdowns of their own and never let up from there.Fellow contenders the Dallas Cowboys were brought back to reality courtesy of a 31-10 demolition at the hands of the Buffalo Bills.The 10-win Cowboys' defence looked powerless against Buffalo's running game, with James Cook, Josh Allen and Latavius Murray all finding the end zone on the ground.Despite the loss, other results from earlier in the day ensured the Cowboys would be in the play-offs for the third straight year.The Cleveland Browns scored 13 fourth-quarter points to snatch a 20-17 victory over the Chicago Bears.The two sides were level at 7-7 at the break after tight ends Cole Kmet and David Njoku scored touchdowns but the Bears took a 10-point lead into the fourth after Tremaine Edmunds returned an interception 45 yards for a touchdown.But the Browns saved their best till last and two Dustin Hopkins field goals partnered an Amari Cooper touchdown to give them the win, with 38-year-old Joe Flacco throwing for 374 yards.Super Bowl champions the Kansas City Chiefs returned to winning ways with a 27-17 victory over the New England Patriots.Running back Jerick McKinnon caught one touchdown pass and threw another to Rashee Rice while Patrick Mahomes threw for 305 yards, two scores and two interceptions.Baker Mayfield [above left] threw for four