Once upon a time, back when dinosaurs roamed the earth and pterodactyls dotted the sky, running backs were the focal point of NFL offenses and bashed heads with big middle linebackers.

But sometime in the past decade, a meteor shower of star quarterbacks crashed into the NFL, changing the landscape and putting running backs and, subsequently, one-dimensional linebackers on the verge of extinction.

OK, so maybe their demise been exaggerated, but as running backs have become devalued during recent drafts, so have the defenders whose primary objective had been to run them down.

"I think it certainly is a case where they have been phased out a little bit in terms of their importance," ESPN's Mel Kiper Jr. said on a recent conference call. "The days where you need that great middle linebacker that can be your run-stuffer, that's just not the case anymore."

The days of middle linebackers being picked early in the draft could become history, too.

During the first round of the NFL draft Thursday night, two pass-rushing outside linebackers, South Carolina's Jadeveon Clowney and Buffalo's Khalil Mack, are considered locks to be selected among the top 10 picks. But Alabama's C.J. Mosley, regarded by many as the top middle linebacker in this class, could be waiting around much longer until Commissioner Roger Goodell calls his name.

The Vikings are one team with a 4-3 defense that could use a playmaking linebacker after waiting to address the position a year ago. Instead of using one of their three first-round picks to plug a prospect such as Notre Dame's Manti T'eo into the middle of their defense, they bolstered other positions. On Day 3, they selected Penn State's Gerald Hodges and Michael Mauti.

"It's always tough to project the development of young players when a new staff comes in, but I do see this as a position to address," said Matt Miller, the lead draft analyst for Bleacher Report. "If Khalil Mack or C.J. Mosley is available, the team has to consider either one of them."

The Vikings likely would be delighted if Mack, an edge rusher who also can defend the run and drop into coverage, was still on the board at No. 8 overall. But is Mosley, who draft analysts say is a three-down linebacker but not much of a blitzer, the rare three-down middle linebacker who is worthy of a top-10 pick?

Not including edge rushers, only seven linebackers have been selected in the first round the past five years, and just three went in the top 10 picks. It paid off for the Panthers, who took Luke Kuechly, the reigning NFL defensive player of the year, ninth overall in 2012. The two others, Rolando McClain (Raiders, 2010) and Aaron Curry (Seahawks, 2009), already are out of the NFL.

The first middle linebacker to come off the board last year — also the first time in a half-century that a running back wasn't selected in the first round — was Alec Ogletree, who went to the Rams at No. 30 overall.

For comparison sake, in 2006, the year the Vikings selected strong-side linebacker Chad Greenway with their first-round pick, four non-rushing linebackers went in the first round.

Bart Scott is only five years removed from the Jets signing a $48 million contract, the kind of deal middle linebackers rarely receive now. Scott, who traded his cleats for a microphone last year and is now an analyst for CBS Sports, says "the game has changed tremendously" since then.

"I'm from the era when you had 250-pound, 260-pound middle linebackers, the big thumpers," he said. "And then you had the athletic guy who played [weak-side linebacker]. Essentially, what's happening is the 'Will' is becoming the 'Mike', a guy who can run from sideline to sideline."

Even former teammate Ray Lewis, the seemingly ageless middle linebacker who is one of the greatest to play the position, sensed the game was changing before his final NFL season in 2012. He lost about 20 pounds so he could try to keep up with pass-catching backs and athletic tight ends, ensuring that the Ravens would keep letting him play every defensive snap.

"You're asking linebackers to do different things," said Greenway, who isn't buying the notion that the position has been devalued. "You have tight ends now that are splitting out and are basketball players turned receivers. It's turned into a different kind of game."

Scott also pointed out that today many teams employ a committee approach at linebacker. Depending on the down and distance, defenses either will use one of those big thumpers or replace him with a coverage linebacker. Some teams, such as the Bengals when new Vikings coach Mike Zimmer ran their defense, sometimes use a third safety instead of an extra linebacker on passing downs.

"It's all about roles," Scott said. "The league has become about situations."

But despite the deep impact of NFL passing offenses threatening to wipe out middle linebackers as early first-round picks, Zimmer is one who believes the rare every-down standouts will continue to be coveted.

"Seven, eight, 10 years, you were looking for the big plugging linebackers that didn't cover as well. Nowadays, you are looking for guys that have a little bit more coverage ability," Zimmer said. "I don't think that the position has become devalued, but it is harder because offenses don't allow you to play one-dimensional linebackers on all three downs."