When the Vikings play Cover 2, the middle linebacker is called the "middle-read" defender. He isn't asked to channel his inner Deion and run stride for stride with a wide receiver 30 yards downfield. It only looks that way sometimes.

"It's not like I'm flipping my hips [like a cornerback] and taking the guy man-to-man all over the field," Vikings strong-side linebacker Chad Greenway said. "If I was that fast, I'd be playing receiver."

With about an 8-yard head start, the middle-read defender drops as deep as the deepest receiver in his zone and simply tries to create a difficult angle for the quarterback. Only it's not that simple when you're 250 pounds or so.

"Basically, you're trying to buy air time on the pass," middle linebacker Jasper Brinkley said. "If the quarterback has to loft the ball over you rather than throw a line drive, that's air time for the safeties [who are playing two-deep coverage] to come make a play on the ball."

All three of the Vikings' starting linebackers have some middle-read duties in Cover 2 calls. Brinkley plays it the few times that it's called in the base defense (three linebackers). Greenway plays it in the dime (one linebacker). And Erin Henderson plays it in the nickel (two linebackers).

Henderson drew unwanted attention to the Cover 2 scheme when the Colts' Reggie Wayne beat it badly for a 30-yard touchdown with 7 seconds left in the first half of the Vikings' 23-20 loss at Indianapolis on Sunday. Henderson's mistake was subtle, but illuminates just how ridiculously difficult it is to play linebacker in a pass-crazed league that has even rookie quarterbacks operating out of an empty backfield with four- and five-wide sets.

Henderson was 8 yards behind the line of scrimmage and dropping when the Wayne touchdown play began. Wayne was the near receiver in a tight two-bunch set to the right. Cornerback Antoine Winfield was in press coverage and shadowed Wayne 10 yards downfield before releasing him inside to Henderson.

Henderson was doing everything right in his deep drop until he reached the 9-yard line. That's when he hesitated and sneaked a peak toward quarterback Andrew Luck. That's a no-no, especially when the guy running full speed at you is the 15th-leading receiver in NFL history.

"I got nosy," said Henderson, "and he kept running."

The slight separation was all Luck needed. His dart split safeties Mistral Raymond and Harrison Smith at the goal line.

Coach Leslie Frazier, a Tony Dungy disciple and therefore a huge proponent of the Cover 2 scheme that's considered antiquated by some critics, defended the scheme.

"You do it because you've done it enough to where you know that the linebacker can make the play, along with safety help," Frazier said. "And we got neither in that instance."

Vikings linebackers coach Mike Singletary is a Hall of Famer and one of the best middle linebackers in league history. When Buddy Ryan, his defensive coordinator with the Bears in the early-to-mid 1980s, perfected his famed quarterback-crushing "46" defense during Chicago's Super Bowl-winning season in 1985, Singletary was ahead of his time as a middle linebacker who was sometimes asked to play deep middle coverage.

"The key is trusting your reads and not getting fooled on the play-fake," Singletary said. "The offense is always trying to fool you, get you to hesitate so the receiver can get by you. That's tough for a linebacker to do. Buddy originally designed the '46' as a nickel defense with a safety playing in the middle. But then he figured he could do it with regular people at linebacker."

Of course, calling Singletary "regular" is a monumental stretch. Unless "regular" means eight-time All-Pro and two-time NFL Defensive Player of the Year. Few have the skills he had. Or the skills of a Brian Urlacher, who made the Bears' Cover 2 scheme dominant in his prime.

"It's a different game now for all linebackers," said Frazier, who played cornerback in the Bears' "46" defense. "Even 10 years ago, you were looking for guys who were in-the-box linebackers.

"Today, those guys have almost gone by the wayside, whether you're a Cover 2 team or not. Those linebackers, particularly the outside backers, are pretty much a hybrid safety/linebacker."

That's why the Vikings made Greenway one of the highest-paid 4-3 outside linebackers in NFL history when they signed him to a five-year, $41 million deal with $20 million guaranteed before last season.

"It's definitely not easy," Greenway said. "But it's just part of the job description in today's NFL."

Mark Craig mark.craig@startribune.com