This is the biggest weekend of football for players on four teams because it will determine if they continue to chase their ultimate goal of the Super Bowl or are sent home, falling just short of a shot at the championship. The NFL’s final four features the Baltimore Ravens going into Foxboro and attempting to knock off the Patriots, and a rematch of two tough defenses at Candlestick Park, where the San Francisco 49ers will be hosting the New York Giants.

Baltimore Ravens at New England Patriots

It doesn’t have a great, long history like the Packers-Bears or Chiefs-Raiders rivalries do, but the Ravens-Patriots rivalry has had important games on some of the biggest stages, whether it be on Monday Night Football, when New England looked to continue its run for a perfect 2007, or in the wild-card round of the 2010 playoffs, when Baltimore emphatically won.

This time around, it’s different for the Patriots. New England doesn’t have Randy Moss, but it still has Wes Welker, who is better than ever. Along with Welker comes Rob Gronkowski, a freak-of-nature tight end who the passing offense appears to be centered around. Gronkowski has developed into the ultimate weapon in New England, lining up everywhere and doing everything. Oh, and there’s a fellow by the name of Aaron Hernandez, who is also a tight end and is pretty good in his own right.

On the other side of the matchup are the Baltimore Ravens, a team that is still questioning whether it has found the right quarterback with Joe Flacco and is yet again heavily reliant on a running back. But this isn’t just any running back. Rice is a 5-foot-8, 212-pound bowling ball.

Intimidating, right?

Rice may be small, but he packs a punch and has shown it on more than one occasion, such as the last meeting against the Patriots when he ran for nearly 160 yards. He can also tote the rock, as NFL scouts say in football parlance.

But Rice isn’t the only thing buzzing in Baltimore. There’s also what seems to be a never-ending tough defense that is still led by Hall of Fame defenders Ray Lewis and Ed Reed. Reed is banged up, yet he’s still making more plays than your average safety. He has a history with the Patriots, who are coached by Bill Belichick — one of Reed’s long-time admirers. Belichick admitted to this in a documentary of his life in football, aptly titled A Football Life.

“Everything he does at an exceptional level.  I mean its just so obvious when he’s reading the quarterback. Those recievers will run right past him and he never flinches. He doesn’t even acknowledge them. He’s just reading the quarterback.”

As Belichick notes, Reed is a bit of a gambler, taking his eyes off of his assignment and focusing on the football, tracking it with this exceptional range. Because of his ability to cover ground so quickly, he gives the defense flexibility in their coverages, and more importantly, their disguises. Disguising coverages is important in football because it causes confusion for the quarterback, who expects something specific based off of hours of film study, yet is befuddled once he sees something unexpected. This will be one of the keys to the Ravens’ defensive success when they face the standard at the quarterback position, Tom Brady, this weekend.

The Ravens defense has had success before against Brady, such as the aforementioned 2010 wild-card game in which they intercepted the Patriots signal caller not once, not twice, but three times in a 33-14 win. One of the defenders Brady found was Reed, who didn’t even care to cover the slot receiver coming in his Cover 2 zone, rather tracking the ball in the air and turning what is usually a simple pass breakup into an interception, as seen in the video below.

This was the case once again against the Houston Texans this past weekend, when the Ravens were in what appears to be a Cover 1 Robber concept with Reed in the middle of the field. Texans quarterback T.J. Yates attempted to manipulate Reed with his eyes, trying to move him to his left before throwing the ball right to wide receiver Andre Johnson.

It didn’t work because of Reed’s football intelligence and eyes. With no movement being made by Reed to Yates’ left, the pivot attempted to drop the ball over the top of the cornerback and away from Reed to the right. Unfortunately for him, Reed’s incredible range allowed him to make up ground and he was able to track the ball all the way through, ultimately catching his eighth career playoff interception.

One thing’s for sure: Tom Brady will be looking for Reed every time he breaks the huddle because “Ed Reed is Ed Reed.”

New York Giants at San Francisco 49ers

Potent offenses appeared to be taking over the NFL this season, with the likes of Green Bay and New Orleans lighting up scoreboards. Yet, as fans prepare for their football weekend, neither of those teams are taking part in the conference championship games. Maybe defenses still do win championships?

It appears to be that way at least, with the San Francisco 49ers’ defensive prowess competing against the New York Giants and their abundance of pass rushers. Both of the defensive trenches have been an integral part of the success of the two teams, especially the 49ers who are led by Justin and Aldon Smith (not related, and henceforth refereed to by first name only).

Justin has been a force this season, terrorizing pass blockers and burying quarterbacks, while Aldon’s power and explosiveness has been too much to handle for blockers of all sorts. While the two pass rushers have a plethora of physical talent, their success has also come through quality schematic design by defensive coordinator Vic Fangio.

Fangio has employed several different fronts and personnel packages to disrupt offenses, but none are more dominant than his stunt packages, which have created one-on-one matchups for Aldon. The X stunt package, as I call it, is often run by the 49ers and requires Smith to administer a stunt to the outside from his inside or head up alignment.

If Justin is aligned in a 3-technique (outside shoulder of guard), he is required to stunt across the face of the tackle and out to the C gap, which is different than a stunt from a head up alignment. In the latter, which is seen in the image below, Smith stunts into the B gap in an attempt to occupy the guard and tackle. His alignment causes a bit of confusion for the tackle, who wonders what his assignment is if the guard is occupied. With no running back behind him to pick up, the tackle must decide which Smith he’ll block. If he takes Justin, Aldon has a free path to the quarterback. However, the same may hold true if he blocks Aldon and the guard is occupied by the stand-up rusher (91) to the left.

Justin Smith causes confusion for the left tackle with his alignment.

Fortunately for him, the guard is free to help out once the stand-up rusher (91) stunts away from him. However, Justin complicates matters for the two blockers (guard+tackle) with a bulrush right in between them at the snap of the ball. By doing this, he occupies their attention and allows Aldon to loop around into the A gap (area between center and guard).

Smith loops free into the A gap with the Guard distracted.

Once the Guard recognizes Aldon, it’s too late as he’s already dipped his shoulder and bent his knees– two things he’s exceptional at —  to create a clearer path to hobbled quarterback Ben Roethlisberger.

The left guard is too late getting to Aldon Smith, who tears through the interior.

This stunt package is one that has had a lot of success this season because of the power of Justin and the flexibility of Aldon. It is something that will be important to watch in this weekend’s game because Eli Manning is primarily a pocket passer, and the best way to pressure a pocket passer is through the interior of the pocket, which is something I expect the 49ers to focus on.