Through three games in 2015, Anthony Walker has been Northwestern's best and most active playmaker on defense. The sophomore middle linebacker seems to be everywhere, using his combination of size, speed and instincts to shut down opponents.

Walker, interestingly, has the "sideline-to-sideline" speed that coaches and analysts dream about but, at times, plays more like a downhill thumper in the middle of the defense. That versatility has allowed Walker to follow up on a promising freshman campaign, leading No. 17 Northwestern to a 3-0 start with wins over Stanford and Duke. Currently, he leads Northwestern in, among other categories, total tackles and tackles for loss.

Northwestern head coach and former All-American linebacker Pat Fitzgerald has been impressed with Walker, but, as is customary, refused to praise Walker too highly in public, instead giving him a back-handed compliment in front of the media this week.

"He's been pretty darn good unblocked," Fitzgerald said during the week following Northwestern's 41-0 win over Eastern Illinois. "I think he's going to get blocked a few more times now."

While that may be a taking a bit of the credit away from Walker for his hot start to the year, it raises a good point about the defensive line's roll in Walker's success.

He's said as much.

"The key to being a great linebacker is to have a great defensive line," Walker said after a practice this season. "That's one thing Coach Fitz told me since day one. You can't be great unless your d-line is great. So you have to keep those guys happy and feed them a little bit. Those guys will take care of you. I try to make sure them guys are happy and they make their plays as well. As long as we are all out there playing on one accord, I think it's perfect."

In Northwestern's season-opening win over Stanford, for example, Walker was a star. He garnered Big Ten Player of the Week honors with his 10 tackles, three tackles for loss, a half sack, two pass breakups and one fumble recovery.

But much of his success was spurred on by the play of the defensive line to not allow Stanford's offensive front to get to Walker.

Take this play, for instance, when Walker darts into the backfield with Deonte Gibson to stop Stanford's Christian McCaffery.

This first thing that pops out is Walker's quick burst toward the ball carrier. It's impressive how quickly he makes the read, locates the hole he needs to fill and bolts toward the tailback. But, after looking closer, this play is more about the defensive line.

Right after the snap, Northwestern's front four is able to force the Cardinal offensive line backwards. On this play, Stanford's right guard is pulling around the left side of the formation and the push Northwestern's defensive line gets inhibits the pulling guard's ability to get around the line to stop Walker. Each defensive lineman won his individual matchup on the play, giving Walker the opportunity to make a play in the backfield.

Here's a similar play run to the opposite side of the field by Duke:

Again, a guard pulls to the opposite side of the line to create a crease but defensive end Dean Lowry gets into the backfield so quickly that the pulling guard has no chance to catch him. Duke signal-caller Thomas Sirk, making the right read, does not give the ball to the running back, instead keeping it himself due to Lowry's pressure.

But Walker is also streaking through the middle of the line unblocked as the other Duke lineman were occupied by the other three defensive linemen. Sirk, thus, has nowhere to go and is taken down for a loss.

Plays like that from Lowry and Walker give one another the confidence to be aggressive against the run. On this read option, for example, Lowry and Walker have both Sirk and the running back sealed up before a read can even be made:

Lowry knows he is the player Sirk will read on these types of plays. But, confident that Walker will be able to make a stop in the middle, Lowry is able to completely sell out to force Sirk to give the ball up. And when he does, Walker is waiting with open arms for the tailback as he, again, has an unblocked lane into the backfield as two Duke lineman have to block defensive tackle Greg Kuhar.

While those types of plays were most frequent against Stanford, Eastern Illinois and Duke, there were also some cases that showed how losing the battle up front can take Walker completely out of a play.

The play starts off with Walker making a good read. He doesn't fall for McCaffery's counter step, and goes right for the hole. Problem is, the right side of Stanford's line gets a great push on Northwestern's front. Instead of meeting the ball carrier, Walker hits a Cardinal wall and is taken completely out of the play.

That's one way to take away Walker's pursuing ability. Stanford is a team that is unafraid to reveal where a play will go as they trust that their blocking will overpower the opponent, even if they know what's coming. Walker knew what was coming, but the right side of Stanford's offensive line over powered Northwestern's defensive front, allowing them to push into the second level.

Overall, the combination of Walker and Northwestern's front four has keyed stellar defensive performances over a downhill running team in Stanford and a spread option attack in Duke. Sure, Walker has been getting the attention and accolades thus far, but the opportunities he has been given this season to play to his strengths — speed and pursuit in the open field — are most often due to the actions of the players down in front of him. Without them playing at a high-level, Walker's talent could be going to waste.