MNF: 49ers at Cardinals

The NFC West takes over Monday night football, and this season at least that means defense. Going into last weekend, the four NFC West teams ranked among the top nine in the league in defense. San Francisco leads the way at No. 1 with a powerful, smash-mouth group that overwhelms opponents, particularly with its excellent front seven. Arizona counters with a fast, aggressive unit that rates No. 7 in the league. Defense could well decide the outcome when the 49ers, looking to break open their lead in the division, face the Cardinals, looking to stop a three-game losing streak with one of the worst offenses in football. ( 5:30 p.m., ESPN)