The only thing that might be harder than defending Percy Harvin is defining Percy Harvin.

Is he a receiver in a running back's body? A running back playing receiver? An elite return man who can run and catch, catch and run or just plain run?

Yes, yes and yes.

But does the Vikings' 21-year-old rookie remind you of any other NFL player you've ever seen?

That simple question got a lot of blank stares after Sunday's 36-10 rout of the Bears at the Metrodome.

"Not to my recollection," Vikings coach Brad Childress said. "Not in my coaching career."

Harvin took another step toward winning NFL Offensive Rookie of the Year with 146 yards and one touchdown on eight touches from scrimmage, including his first 100-yard receiving game (101). In doing so, he outplayed his closest competitor for the honor, Chicago's Johnny Knox, who had a 24-yard touchdown catch and a 77-yard kickoff return to open the second half.

"Percy is on his way to a league of his own," Vikings quarterback Brett Favre said. "He's quick, like a [Patriots receiver] Wes Welker, but I think he's stronger. I think he has a long way to go to be in the same category as Wes. But at the rate he's going, he's a dominant force in a lot of ways."

As former Vikings defensive lineman Bob Lurtsema pointed out after the game, Favre "makes all these different weapons like Harvin click." The Vikings offense had 17 plays of at least 12 yards Sunday. Of those, 15 were passes from Favre. By comparison, the Bears had just three plays of at least 12 yards.

Of Harvin's eight touches, six went for at least 12 yards. Five of them were receptions. One was a 35-yard run after he lined up as a running back to Favre's left.

Harvin also had a 17-yard catch on third-and-7, a 12-yard catch on third-and-7, a 22-yard catch on first-and-20 and the best one of all, a 31-yard catch on third-and-8. The latter was yet another reminder to the rest of the NFL that a soft zone in the deep middle is a Favre-to-Harvin big play waiting to happen.

Bears middle linebacker Hunter Hillenmeyer was the poor soul Sunday whose assignment was to stay close enough to Harvin in deep middle so that Favre wouldn't be tempted to throw there.

As former Vikings running backs coach Dean Dalton said after the game, "That was the mismatch of the century right there."

That's what Harvin does. He creates mismatches that Favre can spot quicker than a 12-point buck.

"This game is about matchups," Harvin said. "Brett does a great job of helping us create the matchups and giving us time to work them."

Harvin then delivered a zinger to Favre, who was standing nearby.

"He's old enough to be my dad," Harvin said. "But I thank God for playing with him."

Now let's get back to that question. Does Harvin remind people of anyone who played before him?

"I'd say Google Gary Anderson, the former Charger," said longtime Dallas Morning News NFL reporter and Pro Football Hall of Fame voter Rick Gosselin, referring to the 1986 Pro Bowl running back.

Gosselin also threw out the names of former three-time All-Pro running back Eric Metcalf, who holds the league record for most punt returns for touchdowns (10), and former running back and 1979 Pro Bowler Joe Washington.

Scott Studwell, Vikings director of college scouting, said comparisons to Panthers receiver Steve Smith, a stocky but fast Pro Bowler, kept coming up when discussing Harvin before the draft.

Vikings offensive lineman Artis Hicks was at a loss, and he used to play with Philadelphia's multitalented Brian Westbrook.

"It's scary," Hicks said. "I can't think of a single guy who I can say, 'Percy is like so-and-so.'"

Harvin should know whom he compares to, right?

"I guess the closest would be Marshall Faulk and the guys who could split out wide," said Harvin, who has seven TDs (five receiving, two kickoff returns). "But I think I'm different."

That much is becoming obvious.

Mark Craig • mcraig@startribune.com