SAN FRANCISCO — The late, great 49ers defense finally showed up.
You know, the 49ers defense that was supposed to knock over offenses, steal the football and unleash hell.

The 49ers defense of Patrick Willis, Justin Smith, Parys Haralson, Dashon Goldson and other swarming playmakers.
The 49ers defense that expected to sweep through the NFC West in 2009 (and didn’t).
During Monday night’s 24-9 throttling of Arizona, while the 49ers offense meandered a bit, their defense was everywhere, doing everything, looking like it had the talent and will to take the team to the playoffs by itself.
Where was that all season?
“We just wanted to go out and prove to ourselves that we could do it,” said linebacker Ahmad Brooks, who had three sacks and two of the 49ers’ team-record five forced fumbles.
“We need a little help (to make the playoffs), but we still believe we can make it.”
It’s probably too late for that. To beat out Arizona (8-5) in the West, the 49ers (6-7) have to win their final three games and still need the Cardinals to lose twice. Unlikely.
But the 49ers’ defensive feeding frenzy on Monday was a large national-TV message to themselves and the rest of the league.
They have established talent (Willis, Smith) and emerging (free safety Goldson was, by far, the best player on the field Monday).
They have speed and toughness. They haven’t given up. It just took 12 games for the 49ers to display it all against a playoff-level team.
Which was about a month too late.
“We knew we had four games left to show what kind of team we can be,” Willis said.
The 49ers captured five Arizona fumbles, snared two interceptions, thrashed quarterback Kurt Warner for four sacks and exuded the loud smashmouthiness that Mike Singletary long ago promised.
Seven forced turnovers, leading to all 24 of their points. A complete mauling of the high-powered Cardinals offense. Total dominance.
“I was just thinking, ’Wow.’ That was all I could say,” Singletary said. “They just kept coming up with plays.”
The ringleader on Monday: Goldson, a first-year starter at free safety who was a singular nightmare for Warner and all Arizona ballcarriers.
Goldson knocked the ball loose from Tim Hightower deep in Arizona territory to set up the 49ers’ first score, intercepted a pass from Warner two series later and forced another fumble in the third quarter.
Arizona’s first-half possessions went like this: three-and-out, lost fumble, lost fumble, interception, three-and-out, interception, lost fumble.
The 49ers offense only needed to travel 8 yards for their first touchdown, 28 yards for their following field goal and 68 yards for the Michael Crabtree TD reception that gave them a 17-0 halftime lead.
The 49ers’ five forced turnovers in the half tied the franchise record for most turnovers in a first half, set in 1997 against New Orleans.
The rest of the game was handled by a revived Frank Gore (167 yards rushing) and, of course, that churning defense.
Running the ball. Great defense. Yeah, I think Singletary can live with that formula.
This was precisely how the 49ers defense thought it would play all season, and, to this point, had displayed only in flashes.
Coming into the game, the 49ers were the 27th-ranked pass defense in the NFL. On Monday, they badgered Warner (44.9 passer rating in the game), Larry Fitzgerald and Anquan Boldin into submission.
Maybe something about the Cardinals brings out the best defensive intensity and strategy in the 49ers, who swept Arizona this season and made Warner look wobbly in both games.
This is the same defense that was counted on to carry this team but was spun in circles by Atlanta, Green Bay, Tennessee and Houston.
At some point, the 49ers defenders and coaches will have to ask themselves: Why did this take so long?
But it happened, once, when the nation was watching and when they had one last shot at Arizona.
Most of all, it was a reminder of what the 49ers always knew they could have been this season and pulled off only when it was too late.