STANFORD, Calif. -- With linebackers Shayne Skov and Trent Murphy off to the NFL and defensive coordinator Derek Mason and inside linebackers coach David Kotulski off to Vanderbilt, change is inevitable for the Stanford defense.

For some, that's code for "worse."

A.J. Tarpley, who was the 2009 Minnesota Gatorade Player of the Year, has been a key cog in the Cardinal's defense for the past three seasons. Tony Medina/Getty Images

Not for fifth-year senior inside linebacker A.J. Tarpley.

"Great players leave. We're not going to lower our goals," he said. "We're not going to say, 'OK, we're not going to be as good as last year.' I want this linebacking corps to be better than last year.

"I do feel that our linebacking corps has gotten better every year since I got here, so why not? Why can't we be be better than we were last year?"

Tarpley wasn't looking for a literal answer, but if he were, the fact that Skov was one of the nation's best inside linebackers and that Murphy led the nation in sacks would be on the list. Those aren't guys who simply get replaced without some level of drop off.

That isn't lost on Tarpley, either. He, perhaps better than anyone, understands just how valuable Skov and Murphy were to the Stanford defense. The part that isn't understood as well beyond the Stanford locker room is how Tarpley's role has been nearly as vital to the Cardinal's success over the past three seasons.

"We see it all the time and we've just marveled at how solid he is, how efficient he is," new defensive coordinator Lance Anderson said. "I think playing next to Skov is a reason he's been a little overshadowed, and then with Trent Murphy and Chase Thomas on the outside the last few years I think it's easy to get overshadowed."

Over the past three seasons, Tarpley is the Cardinal's leading tackler (216). If he replicates his 2013 total (93), he'll finish his career in the top 10 on the school all-time tackles list. Currently, only two other players who began their career in 1990 or later are part of the group: Skov (2009-13) and Chris Draft (1994-97).

Tarpley's near-immediate production came as no surprise to Stanford coach David Shaw, who said the former Minnesota Gatorade Player of the Year made a strong impression during his true freshman season during the team's scrimmages on Fridays.

"He just seemed to make every play," Shaw said. "Tackle after tackle after tackle, and if the ball was thrown anywhere around him he either picked it off or deflected it."

Both Shaw and Anderson credited Tarpley's instincts as a major factor in his success, which, coupled with good quickness, makes up for what wouldn't be described as elite athleticism. Anderson has Tarpley down for 4.75 seconds in his most recent 40-yard-dash.

"There's a lot of people that think I study tremendous amounts of film and know what plays the offense is going to run, but that's not the case," Tarpley said. "I believe I'm a pretty good athlete. I base everything off my quickness and just read plays to make things happen."

And if film study isn't the root of his ability to read defenses, what is? That's simple: video games -- the Madden franchise, in particular.

Tarpley is a firm believer that playing Madden -- a game in which he claims he's unbeatable -- has helped develop his understanding of the way angles, routes and coverages work.

"Looking at the plays in Madden you see passing concepts, you see zone coverages and how those work out ... where this guy is and who he's replacing and how things can occur," he said. "I really do think going through the plays on both offense and defense -- what beats what? -- I think that's helped me as a player. When I'm out there on the field, it's almost a [subconscious] decision in my mind how something should develop."

That understanding has allowed Stanford to regularly use him to cover receivers in single coverage with good results. Tarpley is the program's only player to record an interception in each of the past three seasons.

"He is one of the best coverage linebackers I've been around," Anderson said. "He has such good patience and a good feel for routes and what people are going to try and run. That is one thing that stands out. I don't know if I've been around anyone like him like that."

Tarpley's focus is on finishing his Stanford career strong, but he made it clear the NFL is also in his sights.

"I've always been doubted my whole career. No one's ever said how great I was going to be so I've always had that mentality with a chip on my shoulder," he said. "I'm going to dream about [playing in the NFL] every day until I can earn a spot there."

And if that doesn't work out, there's always the Madden pro leagues to fall back on ... or his Stanford degree.