A few thoughts on the San Francisco 49ers' defense matching up against the New England Patriots' offense in Week 15:

2012 Tom Brady Passing

Pressure tactics. The 49ers rely on standard pressure 80 percent of the time, tied for fifth-highest. That means they send more than four pass-rushers on 20 percent of dropbacks. The approach sets up well against New England. Patriots quarterback Tom Brady is good just about all the time, but he's particularly dangerous when teams trade coverage for pressure. Brady has 18 touchdowns, no picks and a 92.2 Total QBR score against five-plus rushers. As the chart at right shows, Brady is actually tougher to sack when teams come after him with additional rushers.

Trouble in the slot. Patriots receiver Wes Welker is a tough matchup for most teams. The 49ers' struggles against the St. Louis Rams' Danny Amendola comes to mind here. Amendola caught 11 passes for 102 yards against San Francisco in Week 10. He was trouble for 49ers slot corner Carlos Rogers. Welker fits the same mold. The 49ers might need to double-cover Welker. Fortunately for them, New England remains without injured tight end Rob Gronkowski. Before Monday night, Welker had caught 31 of 35 passes for 443 yards and two touchdowns from the right slot. He had more than double the targets from there as from anywhere else.

What has worked. The Miami Dolphins held Brady to 4 of 15 passing with two sacks and a 4.4 QBR score on first down, including 3 of 11 when rushing four or fewer defenders. Arizona was one of the few teams to succeed against New England while pressuring. Brady completed 1 of 4 passes for nine yards on third down when the Cardinals rushed five or more. However, the Patriots lost tight end Aaron Hernandez to injury in that game, affecting their plan. Overall, Brady has completed 25 of 33 passes with seven touchdowns, no interceptions, three sacks and a 98.1 QBR score when teams pressure him on third down.

Searching for weaknesses on Brady isn't very satisfying. I've been looking through his numbers from various personnel groups on various downs against various defensive personnel. Not much jumps out as a clear vulnerability.

Pats' Yards After Catch/Reception by Opp.

The 49ers will of course need to pressure Brady with four-man rushes. A big game from NFL sacks leader Aldon Smith would certainly help. He has 15 sacks in his last seven games and 19.5 for the season.

San Francisco will also want to punish Welker and the other receivers after the catch. Brady is going to complete a high percentage of passes, most likely. There must be a price.

Seattle and Arizona fared well in limiting yards after the catch against New England. They also beat the Patriots. Getting Welker and teammates to the ground quickly could be a must against an offense as efficient as this one.

The 49ers rank seventh in yards after catch allowed per reception (2.7). Pittsburgh (2.4), the New York Jets (2.5) and Seattle (2.5) lead the league.

The chart below shows the Patriots' QB stats by opponent. Ryan Mallett completed 1 of 4 passes for 17 yards with one interception against the Houston Texans on Monday night.

2012 New England Patriots QB Play by Opponent QBR Allowed