FOXBOROUGH, Mass. -- Top linebackers Ahmad Brooks of San Francisco, Lavonte David of Tampa Bay, Tamba Hali of Kansas City and Luke Kuechly of Carolina play all three downs.
So do Philadelphia's four starting linebackers; DeMeco Ryans played 1,189 snaps last season, the most of any NFL defensive player. That's more than 74 snaps per game.
Now his workload may be reduced.
"I've said, 'Look, I know you want to be out there every down, everybody does. But I'm telling you right now that I'm going to work to get some ways to give you some relief to have you with us in Week 15 and 16,'" Eagles defensive coordinator Billy Davis said, "and he's great about it."
Hall of Fame linebacker Andre Tippett had a simple answer for how often he left the field when the opponent had the ball.
A slight exaggeration? Perhaps.
What's certain is that an NFL linebacker's role has changed since Tippett's retirement after the 1993 season ended a 12-year career, all with the New England Patriots, in which he sacked quarterbacks, shadowed receivers, tackled rushers and tried to catch his breath.
In today's NFL, few linebackers are as busy as Tippett. Rules that encourage passing have led teams to replace a big linebacker with a speedier one, or with a defensive back in nickel packages. Some linebackers are used exclusively to rush the passer. Others are used in running situations. And many linebackers are not as well-rounded coming into the league because they have less practice time in college, and even NCAA coaches are using a platoon system.
"That position has been specialized for several years now," New York Giants defensive coordinator Perry Fewell said.
Today's linebackers must tussle with big, fast tight ends. Jimmy Graham, Rob Gronkowski, Greg Olsen, Julius Thomas and Jason Witten all are at least 6-feet-5 and 250 pounds. And who can keep up with super-speedy Vernon Davis?
Through 2008, there was just one season in NFL history, 2005, when at least eight tight ends caught 60 passes or more. That's been done in each of the last five seasons.
In Tippett's 12 years, tight ends caught at least 60 passes just 28 times. In the past three years, 31 have done it.
"Everybody seems to have that special guy that, is he a tight end? Is he a wide receiver? Is he both?" Tennessee defensive coordinator Ray Horton said. "So you do need special people" to cover them.
Few teams have more than two linebackers who play all of the first three downs.
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Last season, only 73 linebackers played more than two-thirds of the league-wide average of running and passing plays.
Just 60 of them, less than two per team, were on the field for more than three-quarters of that amount.
"You look at those Super Bowl years (the 2001, 2003 and 2004 seasons) that we won, we won with the 3-4 defense and most of those guys pretty much stayed on the field," said Tippett, the Patriots director of community affairs and franchise leader with 100 sacks. "It's a badge of honor."
New England coach Bill Belichick recalls having Lawrence Taylor, Carl Banks, Pepper Johnson and Harry Carson in the 1980s when he was linebackers coach and defensive coordinator for the Giants.
"I can't remember too many times when (they) were standing behind me," Belichick said, "but it wasn't very often."
Just like the freedom defenders once had to hit quarterbacks and receivers, those days are gone. And this season officials are cracking down on contact with receivers.
The three-down linebacker "is a dying breed," said Gunther Cunningham, senior coaching assistant with the Detroit Lions who has spent the past 32 seasons as an NFL head coach or assistant.
One of his linebackers, Stephen Tulloch, rarely comes off the field.
"It takes a lot of work in the offseason, taking care of your body to stop the run and defend the pass," Tulloch said, "and a lot of work in season watching film so you can help the team in every situation."
A run-stopping linebacker usually is replaced by a defensive back on third down, especially with the increase in four-receiver formations.
The days of smashmouth football when Dick Butkus patrolled the middle are long gone.
"The evolution you can trace to certain rule changes that make (it) a little bit more advantageous to throw," New Orleans coach Sean Payton said. "You are still looking for big, strong guys that can defend the run on first and second down and have the versatility to play in coverage."
Tippett wouldn't have liked to leave the field.
He has worked in the Patriots' front office since retiring and has teased players in the locker room.
"I say, `You know, I never came off the field. You know that, don't you?'" Tippett said. "Then they'll start laughing a little bit."