LATROBE, Pa. — One of the greatest plays in Super Bowl history apparently resulted from Steelers linebacker James Harrison's guess work, not the Pittsburgh coaches' game plan.

Harrison revealed while reporting to training camp on Friday that he didn't follow his coaches' orders on his 100-yard interception return touchdown that ended the first half against Arizona on Feb. 1 and has quickly become one of the signature plays in any Super Bowl.

Harrison's return of Kurt Warner's pass over the middle intended for Anquan Bolden gave the Steelers a 17-7 halftime lead. They went on to win 27-23 on Ben Roethlisberger's last-minute touchdown pass to Santonio Holmes.

If the Cardinals had scored on the first-and-goal play from the Pittsburgh 2, they likely would have led 14-10 at the half and would have owned the momentum.

"I actually wasn't supposed to drop on that play, I was supposed to blitz," Harrison said Friday. "All night, we were a step late. We had an all-out blitz and I figured if I stepped (out) I could hold my tackle ... (then) I would drop off and they would have to do a quick slant."

Harrison guessed correctly, stepped in front of Warner's pass and took off down the sideline.

The first half clock would have expired if he had been tackled in-bounds, but Harrison shoved the ball across the goal line as Cardinals receiver Larry Fitzgerald pulled him to the turf.

Harrison joked it "took me two weeks to catch my breath after that play."

Harrison said Steelers defensive coordinator Dick LeBeau never questioned why he gambled.

"Technique, opportunity and all that other stuff met (on that play) — and a little bit of luck," Harrison said. "Sometimes you just feel that might be the play that does it. I guess coach LeBeau didn't mind it too much."

Harrison, the NFL Defensive Player of the Year last season, often is a contrarian known for doing things his way, and he did so again Friday. While his teammates mostly piled out of large SUVs or pickup trucks, he pulled up to camp in a Smart car that was only slightly larger than Steelers nose tackle Casey Hampton.

Harrison gave coach Mike Tomlin a ride in the smaller-than-subcompact vehicle that is popular in Europe, where gas prices are much higher than in the United States. And, yes, both player and coach fit in the car at the same time.

"It's not so much the gas mileage ... I just want to do something to help the environment," said Harrison, who said the car was lent by a dealer.