Imagine shouldering a task where you keep pace with speedsters who cover almost 10 yards in a second while running backwards. Imagine, say, on the following play, getting run over and dragged around by a chunk of 250-pound bulk.

That’s exactly the role Northwestern defensive backs take on the field.

“It’s a tough position,” said Raheem Covington, a 5-foot-9, 181-pound cornerback. “You’re going to guess where the (wideouts) are going — they know where they’re going. You’re playing with your natural instincts. It’s tough. You’ve got to react. It’s a special position.”

All year, the NU defensive backs have lived in the shadows of the team’s explosive offense and the conference’s best linebacker corps. But safeties Rashad Morton and Rashidi Wheeler, as well as Covington, follow the Wildcats linebacker trio of Billy Silva, Kevin Bentley and Napoleon Harris in total tackles.

Most importantly, the DBs have improved from last season, when they allowed more than 200 passing yards per game and numerous big plays.

Last year NU allowed four touchdowns of more than 64 yards. The most devastating was Purdue quarterback Drew Brees’ 99-yard bomb to Vinny Sutherland, which cost the Cats last September’s game in the fourth quarter.

And that meant NU defensive backs coach Brad Bolinger didn’t have to think long to find an area for improvement.

“The one thing that we’ve done a better job of this year is we’re not giving up the deep ball,” Bolinger said.

Thus far, Michigan State quarterback Jeff Smoker’s 39-yard completion has been the longest by an NU opponent.

Physical abilities aren’t the only qualifications of a defensive back — a DB has to be smart enough to avoid pass interference flags.

“The thing I think is most difficult about it is that when a DB makes a mistake, everyone in the stands know it,” Bolinger said. “So a DB has to be very, very confident in his abilities, and he has to be able to bounce back if the guy catches the ball because those guys playing receiver are pretty good, too.

“Nobody knows if a guy in front misses his block or someone misses a tackle. That’s why you have to be a little bit different to play defensive back. … The mental aspect of it is very different than a lot of positions.”

Senior cornerback Harold BlackMonday, NU’s career-leader in passes broken up, enjoys the challenge.

“As a corner, you’re not going to be great unless you take chances,” Blackmon said. “When taking those chances, you have to be aware that sometimes they’re not going to be right. It’s a one-on-one matchup.”

Guarding against the run is just as challenging — especially for the safeties. Morton, a 211-pounder, and Wheeler cover the running game when NU’s opponents break through a hole.

Wheeler found out the hard way against Michigan State two weeks ago in going up against 252-pound running back T.J. Duckett.

“I blacked out for a second because he’s a big boy,” Wheeler said. “I went over to tackle him down the sidelines. I just got up and saw turf and blue skies, turf and blue skies.”

There are times when the defensive backs get a pat on the butt and receive a standing ovation. Blackmon has four interceptions this year, including one he hauled in last week off the arm of Indiana quarterback Antwaan Randle El.

Against Indiana, Blackmon further demonstrated the big-play impact of a DB. In the first quarter, he literally took the ball away from an Indiana wideout. Wheeler recovered the fumble, and Blackmon had reason to pat himself on the back.

“The strip — that was hard work,” Blackmon quipped. “I had to put on my thinking cap for that. I think that was a pretty cool play and I’m just thankful that (the ball) came out.”

On Saturday, NU faces Purdue quarterback Drew Brees and the offense that stole the game in the fourth quarter last year. In his game plan, NU coach Randy Walker has focused on stopping the running game before contemplating Brees’ ability in the pocket.

If all follows the Cats’ blue print, almost all of the pass coverage responsibility will be left to the DBs.

“We really have to stop the running game first, and then, force them to pass the ball,” Blackmon said. “Force them to pass the ball, then we can, as DBs, do our job, which is what we’re on scholarship to do out here.”