RENTON – Seahawks coach Pete Carroll warned over the summer that judging Percy Harvin this season might be unorthodox.

“Really good players have always helped other guys play well, and I think Percy’s factor could be one that really does help other guys,” Carroll said in August. “It won’t always be his stats and his numbers.”

In Seattle’s 26-20 overtime win against Denver on Sunday, Harvin caught seven passes, the most on the Seahawks, but for the first time this season he didn’t have a rushing attempt. And yet when Harvin’s name surfaced after the game, Carroll didn’t talk about Harvin’s catches but about his impact on the running game.

Before the snap, the Seahawks brought Harvin across the field in motion and faked handing him the ball seven times — on what are known as “jet” or “fly” sweeps. Even though the Seahawks never gave Harvin the ball, the threat of doing so gave running back Marshawn Lynch more room to run.

“He kept drawing attention, and it allowed us to run the ball inside,” Carroll said. “It was a really significant part of the plan. ... There wasn’t a time to give him the football, but his factor was still felt.”

Since arriving in Seattle via a trade with the Minnesota Vikings before last season, Harvin has had an air of mystery about him. But now that he is healthy and a major part of the Seahawks’ offense, what has his impact been through three games? What is the Percy Harvin Effect that Carroll alluded to?

The Seahawks have lined Harvin up all over — at inside and outside receiver, at running back — and they have moved him around before the snap. If nothing else, that creates more scenarios for which opposing defensive coordinators must prepare.

Harvin is Seattle’s leading receiver with 15 catches for 106 yards, and while his speed stirs images of a deep threat, he often gets the ball on short, quick throws. What makes him valuable is his ability is to turn relatively easy throws into big plays.

Former Chicago Bears general manager Jerry Angelo faced Harvin’s Minnesota teams twice per season, and he said Harvin was the best player on the field each time for that reason.

“I’ve never seen a receiver that strong,” Angelo said. “There’s nobody harder to tackle after the catch than him.”

When the Seahawks motion Harvin and either fake giving him the ball or actually hand it to him, they accomplish several things right away.

In the instant the play is unfolding, they are forcing a safety to move from inside the box near the line of scrimmage to follow Harvin as he runs outside.

“Wherever he is on the field, you’ve got to spy him,” Angelo said. “You’d be foolish not to. You can never just treat him as mortal.”

The Seahawks are also creating uncertainty and hesitation for defenders who aren’t sure if Harvin, Lynch or quarterback Russell Wilson will emerge from the backfield with the ball.

Former NFL linebacker Chad Brown said the first thing he wanted to do was decide whether a play was a run or pass. But by having so many different options unfold so quickly — Wilson can hand the ball off to Harvin, hand it off to Lynch or roll out with it himself, all in a matter of seconds — the Seahawks muddy up that read for defenses.

“They ruin the first couple of seconds of the play because I don’t know what the play is going to be,” Brown said.

Brown played linebacker and defensive end in the NFL, and he looks at how the Seahawks use Harvin and Lynch from that perspective.

If Brown was responsible for containing Harvin on runs outside, he might stay just a little farther outside to make sure Harvin’s speed doesn’t beat him. But if he does that and the Seahawks hand it off to Lynch, he might be a little late to make a clean tackle on Lynch.

“If you’re trying to tackle Marshawn Lynch,” Brown said, “the difference between putting an arm on him and putting a shoulder pad on him is maybe only eight inches. But that eight inches is the difference between him going down and him running through your arm tackle. Or if I’m trying to contain Percy Harvin, if I’m a half-step slow getting out there, I’m no longer in the contain position, and I’m not going to win trying to chase him down.”

But handing the ball to Harvin as he flies across the field also helps the offensive line. By the time Harvin gets the ball, he is already running full speed, and it is highly unlikely that stationary defensive linemen or linebackers will be able to catch him around the edge.

That means the offensive line doesn’t need to win one-on-one battles at the line. The only block that truly matters is the one thrown by the receiver on the side to which Harvin is running.

In the fourth quarter of the San Diego game, for example, the Seahawks handed the ball to Harvin in motion, but receiver Doug Baldwin couldn’t get his block and Harvin was tackled for a 6-yard loss.

“I was on the sideline for the Green Bay game and (saw) how Julius Peppers and Clay Matthews ... were very unsure coming off the ball,” said Michael Robinson, former Seahawk fullback and NFL Network analyst. “They were stopping, they were guessing.

“There were so many things they had to stand and think about, and while they’re standing thinking, Percy’s moving. He’s going. It’s really that simple.”

Jayson Jenks: 206-464-8277 or jjenks@seattletimes.com

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