The veteran official began an annual training-camp rules interpretation session with the Seattle media after practice on Friday by bringing up the subject without being asked.
"It was a tough thing for me. I kicked two calls in the fourth quarter and I impacted the game, and as an official you never want to do that," said the veteran of 15 NFL seasons and two Super Bowls.
"It left me with a lot of sleepless nights, and I think about it constantly," Leavy said of the February 2006 game. "I'll go to my grave wishing that I'd been better."
Several calls went against the Seahawks in their 21-10 loss to the Steelers. It was Seattle's only Super Bowl appearance.
This week is the first time since that game Leavy has been in Seattle with the Seahawks. He and a mini-crew arrived Thursday to help with the team's practices and give it a rules presentation.
Leavy didn't specify which plays he "kicked" that day in Detroit.
"Bill's personal comments speak for themselves and we see no reason to add to them," NFL spokesman Greg Aiello said Saturday.
Early in the fourth quarter, tackle Sean Locklear was called for holding on a pass completion that would have put the Seahawks at the Pittsburgh 1, in position for the go-ahead touchdown. After the penalty, Matt Hasselbeck threw an interception, and then was called for a low block on a play that ended with him tackling Pittsburgh's Ike Taylor on the defensive back's return.
The penalty moved the Steelers from their 29 to the 44. Pittsburgh used its better field position to score the clinching touchdown four plays later.
The next day, then-Seahawks coach Mike Holmgren told fans at a civic gathering at Qwest Field: "I knew it was going to be tough going up against the Pittsburgh Steelers. I didn't know we were going to have to play the guys in the striped shirts, as well."
Holmgren, now a top executive with the Cleveland Browns, has since said he's gotten over that game.
But Leavy hasn't.
"I know that I did my best at that time, but it wasn't good enough," said the retired police officer and firefighter in San Jose, Calif., who became an NFL referee in 2001. "When we make mistakes, you got to step up and own them. It's something that all officials have to deal with, but unfortunately when you have to deal with it in the Super Bowl it's difficult."
Hasselbeck said he and Leavy had a chance to talk last season and address the game.
"I think all of the officials we have in the NFL are stand-up guys and Leavy is no different," Hasselbeck said Saturday.
Bobby Engram, who spent eight seasons with the Seahawks and now is with the Browns, said the team wasn't playing its best that day anyway, on top of the momentum-changing calls.
"But I feel bad for the guy," Engram said. "These refs try hard and I respect what they do. It's not an easy job. It's a fast-paced game and a lot of big, strong guys are flying around. It's just unfortunate that he had a bad game in the Super Bowl."
When high-profile referee Ed Hochuli visited the Seahawks' training camp in the months after that Super Bowl, he and his crew took good-natured ribbing from players.
"The Super Bowl was one of those games where it seemed the big calls went against Seattle," Hochuli said in August 2006. "And that was just fortuitous -- bad fortuitous for Seattle.
"The league felt, actually, that the Super Bowl was well officiated. Now, that doesn't mean there were no mistakes. There are always mistakes, but it was a well-officiated game."
Information from ESPN.com's Mike Sando and James Walker, and The Associated Press contributed to this report.