By Randy Covitz

Tribune News Service

Think of the Pittsburgh Steelers, and images of Mean Joe Greene and the Steel Curtain defenses of the 1970s or James Harrison and the bone-crushing Super Bowl champions of the 2000s come to mind.

Think again.

The 2014 version features the most explosive offense in the NFL but just a pedestrian defense. Now, the Steelers, who the Chiefs face on Sunday (noon on CBS) in a game critical to both teams' AFC playoff hopes, win games in shootouts, not by shutouts.

It's a lot more fun for quarterback Ben Roethlisberger, who is enjoying a career year in offensive coordinator and former Chiefs coach Todd Haley's free-wheeling offense.

"We've got a great group of guys who believe in each other and believe in the system," Roethlisberger said. "(Haley) wants to have a balanced offense, and we are that. We run it, we throw it, we do a little bit of play action, a little bit of screens ... we do everything.

"We take a lot of pride in our offense. Every game since you played pee-wee football, as an offense you always want to score as many points as you can."

The Steelers, 9-5, are scoring points like never before in their 82-year history. They are averaging 27.8 points per game, a pace that would break the franchise record of 26.6 set nearly 40 years ago, in 1975.

The Steelers lead in the NFL in offense with 424.9 yards per game, in time of possession at 33 minutes, 11 seconds; in yards per play at 6.2, in yards per first-down play at 6.54, and have scored 30 or more points seven times.

By contrast, their once-vaunted defense ranks just 19th overall and 25th against the pass. While Roethlisberger has produced two 500-yard passing games and 13 pass plays of 40-plus yards, the Pittsburgh defense has allowed a league-most 15 passing plays of 40-plus yards and have just 24 sacks, ranking 27th in sacks per pass play.

Clearly, the identity of the Steelers has changed.

"Not to take anything away from what they do defensively," Chiefs safety Kurt Coleman said, "but offensively, surprisingly with losing (wide receivers) Mike Wallace and Emmanuel Sanders ... their offense is really running efficiently."

It took Roethlisberger nearly three years to get completely comfortable with Haley, who joined the Steelers in 2012, the season after he was dismissed as Chiefs coach. Pittsburgh went 8-8 and missed the playoffs the last two seasons, and Steeler Nation was growing restless with Haley's game plans and play-calling.

"Anytime you have something new, there's always going to be a feeling-out process, both with a person and a system and the man himself," said Roethlisberger, who had some clashes early on with the tempestuous Haley. "So yeah, that first introduction, trying to figure things out, especially when you've been in one system for a long time."

"Now that I've started to figure it out, we've been able to be on the same page, and we've been able to work together."

Roethlisberger is now so comfortable working with Haley, he already has shattered his own single-season team record for passing yards in a season with 4,415, breaking the mark of 4,328 set in 2009.

His favorite target, Antonio Brown, leads the NFL with 115 receptions, breaking Hines Ward's club-record 112 in 2002. Brown, with an NFL-leading 1,498 yards receiving, is 1 yard short of the team record he set last season, and he's tied Wallace and Hall of Famer John Stallworth with seven 100-yard receiving games for the most in one season in Pittsburgh history.

"I've seen him go against double coverage and beat 'em, I've seen him go against single coverage and beat 'em," Coleman said. "He's a handful."

Yet Roethlisberger, a two-time Super Bowl champion, has gone on record as saying second-year running back Le'Veon Bell is the one having "an MVP caliber" season.

Bell ranks second in the NFL in rushing with 1,278 yards and has produced a whopping 105 first downs (67 rushing, 38 receiving) -- or 12 more than anyone else in the league. Even when a team like Atlanta ganged up on the line of scrimmage and held Bell to just 47 yards in 20 carries last week, he still scored on runs of 13 and 1 yard and caught five passes, giving him 76 receptions.

"He's very graceful," Coleman said. "He reads his blocks, and he's not a guy who is just going to just hit a hole. He's going to be patient ... and I've seen him make some amazing runs.

"What we have to do best is limit their explosive plays, whether that be run or pass. Make them drive the ball down the field ... if it becomes a point battle, we're not doing ourselves any justice."