The San Francisco 49ers have fielded an effective, sometimes dominant defensive line recently, even without factoring outside linebacker Aldon Smith into the line equation.That's why it was shocking to see ESPN's NFL scout, Matt Williamson, rank the 49ers' defensive line fourth among those in the NFC West.Matt Williamson Ranks West by PositionThe No. 4 ranking could be misleading, however. Williamson explained why in kicking off the latest conversation in our series ranking NFC West teams at each position.