So does owner Jed York, and he's giving Singletary nine games to provide it.

Singletary announced no major strategic changes when he was introduced Tuesday as the 49ers' interim head coach. Instead, the Hall of Fame linebacker who replaced Mike Nolan thinks he can reverse the long-struggling Niners' four-game losing skid with leadership and intensity.

Judging by the look in his famously fierce eyes, Singletary's players just might believe it.

"I don't really know ... what button to press here and what button to press there," the former Chicago Bears star said. "I just know what is in my heart. I know that there is a fire that burns in my heart for this team to be successful. And that fire is unconquerable, and it will not die until it comes to pass."

York, the 27-year-old son of the 49ers' principal owners, appeared alongside general manager Scot McCloughan and Singletary for the announcement. His presence was the most significant sign to date of his rise in the club's power structure, and he made an immediate splash when he proclaimed the 49ers lack "passion and intensity."

"We have talent. There's no doubt that we have talent," he said. "We've got Pro Bowlers on all three phases of the ball. What we're lacking right now is that killer instinct, that finishing ability.

"We're not getting outplayed," York added. "We are getting out-intensitied. I don't think that's a word, but I'm going to use it anyway. That's what we need, and that's what Mike Singletary is going to bring. I think you feel it, I assume you feel it. You feel his presence when he's up here speaking. That's what he brings to the organization. That's what he's going to bring out of the players."

Singletary, who got into coaching in 2003 as Nolan's assistant in Baltimore, had mixed feelings about replacing his coaching mentor, fired by the 49ers (2-5) on Monday night seven games into his fourth season. Nolan's 18-37 record was the worst for any 49ers coach who made it through a full season with the club, yet Singletary believes Nolan had the franchise on the right track.

"Right now, the guys realize that we do have something here," Singletary said. "To what degree, I don't know, but we do have something special here. It's a matter of stepping in and being able to bring it together, and that's something I've done all my life."

Singletary's appointment gives the NFL seven black head coaches, matching the most in league history. He's the third coach to take over a club during the current season, joining St. Louis' Jim Haslett and Oakland's Tom Cable.

Singletary had been Nolan's assistant head coach since 2005 with the 49ers. McCloughan said he approached owners John and Jed York "a couple of weeks ago" with a plan to fire Nolan, who hired the executive when the Yorks gave control of all football operations to a career assistant coach with no background in personnel.

When the Yorks agreed, McCloughan didn't even wait until the 49ers' bye next week.

"I don't think there is a right time for a decision like this," said McCloughan, who gained decision-making authority over Nolan last winter after the 49ers' third straight losing season. "If you go off of past experiences and talking to people, the bye week is usually the best week. ... But I think with the distractions on the outside, the most important thing is for us to be ready to play this week, to play against the Seahawks."

Nolan released a brief statement through the 49ers thanking his players for their hard work.

"It is the responsibility of the head coach to build a foundation and an environment for success," Nolan said. "In many areas we were, although it is winning that ultimately determines success."

San Francisco hasn't made the playoffs or had a winning record since owner John York fired coach Steve Mariucci following the 2002 season.

Singletary's intensity and leadership abilities apparently elevated him past offensive coordinator Mike Martz, who took the Rams to the Super Bowl during his tenure as their head coach. While Martz, San Francisco's sixth coordinator in six seasons, is busy each week with the 49ers' game plan, McCloughan believes Singletary can more easily assume the head coach's supervisory role while concentrating on motivation.

That's an area Singletary knows intimately. After his final NFL season in 1992, he dabbled as a motivational speaker and an author while raising seven children with his wife, Kim. After he caught the coaching bug a decade later, he landed a job on Brian Billick's staff in Baltimore alongside Nolan, and the two quickly became friends.

The 49ers also fired offensive line coach George Warhop, one of Nolan's original assistants. San Francisco's line has yielded a league-high 29 sacks this season.

Jason Tarver will take over many of Singletary's duties as the 49ers' linebackers coach. Singletary has been praised for his work with Patrick Willis, the NFL's defensive rookie of the year last season.