PITTSBURGH (AP) -- The Pittsburgh Steelers spent two years rebuilding themselves on the fly, a necessary process that frequently looked more erratic than inspiring.
Consider the project nearly complete. The surging Steelers are heading back to January.
"It was such a sense of urgency this week, knowing what was at stake," defensive end Cam Heyward said. "I just thought we answered the challenge."
Pittsburgh (10-5) faces Cincinnati next week for the AFC North title. Either way, the Steelers are in the playoffs for the first time since Tim Tebow and Denver stunned the defending AFC champions in the wild card round three years ago.
That group was on the tail end of a stretch that saw Pittsburgh put together three Super Bowl appearances in six years. This group is decidedly younger. The Steelers won their third straight and are 7-2 since an October loss at Cleveland left them at 3-3.
Those days suddenly seem long ago. Pittsburgh kept the Chiefs in check behind a resurgent pass rush energized by the return of James Harrison. The 36-year-old linebacker missed last week's win over Atlanta with a knee problem. He returned to pick up 1.5 of Pittsburgh's season-high six sacks.
"We're headed in the right direction," Harrison said.
The Chiefs? Not so much. Alex Smith passed for a season-high 311 yards, but Kansas City lost for the fourth time in five games. The Chiefs need to beat San Diego next week and get some help to make it back to the playoffs for a second straight year under Andy Reid.
Moving the ball wasn't a problem. The Chiefs outgained the NFL's top-ranked offense 327-288 but couldn't seem to get the one momentum-turning play that mattered. Kansas City came in second in the NFL in red zone touchdown percentage only to see six drives into Pittsburgh territory end with four field goals by Cairo Santos, Jamaal Charles' fumble and a fourth-down gamble late in the first half that fizzled.
"There are so many little things that happened," Smith said. "They're not big things, but just little stuff that gets magnified."
That's the case this time of year. And the Steelers, after a brief foray into 8-8 mediocrity in 2012 and 2013, are back playing their best football when the temperature drops. A roster that's undergone a youth movement since a Super Bowl loss to Green Bay four years ago is growing up quickly, though with a few familiar faces leading the way.
The Steelers' win also eliminated the Dolphins from the playoffs as the crowded AFC field thins. Pittsburgh heads into the final weekend of the regular season with a postseason spot assured. The only question now is the destination.
Roethlisberger wasn't as dynamic as he's been at times this season but led a pair of long touchdown drives. The second ended with a 3-yard strike to Antonio Brown that gave Pittsburgh a 17-6 lead late in the third quarter. Roethlisberger briefly went to the locker room with a right knee injury but returned after a Kansas City field goal to guide a 12-play, 70-yard march that ended with Shaun Suisham's 23-yarder with 4:04 remaining to all but clinch it.
A team that struggled closing out opponents early in the year has won three straight, with each one featuring a dominant finishing kick.
"You can see us cutting down the mistakes," Bell said.
Instead, the Chiefs flinched, though not for lack of imagination. Kansas City put together a successful fake field goal in the first half that extended a drive but didn't lead to the end zone. Trailing 10-6 late in the half, the Chiefs drove to the Pittsburgh 12 and faced fourth-and-inches with 27 seconds to go.
Rather than opt for a chip-shot field goal that would have trimmed the deficit to a point, the Chiefs went for it. Charles was drilled by Lawrence Timmons behind the line of scrimmage, and when Will Allen piled on, the Steelers had the ball and the momentum with a postseason berth just 30 minutes away.
"When your back is to the wall, it shows what you're about and what you stand for," Timmons said. "That was huge for us."
NOTES: Brown finished with seven receptions for 72 yards. He now has 122 catches on the season, the third-highest single-season total in league history. ... Charles was held to 29 yards rushing on nine carries, his second-lowest total of the season. ... Pittsburgh has won six straight games in December.
Online: http://pro32.ap.org/poll and http://twitter.com/AP-NFL