But few needed to understand. They've seen him run.
"He's a very dangerous man," Steelers coach Mike Tomlin said of the back who, at 4.24 in the 40, is tied for the all-time fastest electronic time at the NFL combine.
Johnson hit the NFL in 2008 and led the league in rushing in 2009 with 2,006 yards.
He began that season with a 15-for-57 performance against the Steelers and ended it with 11 consecutive 100-yard games.
Johnson opened the 2010 season with another 100-yard game, and with 12 straight was shooting for the record of 14 held by Barry Sanders. But the streak was stopped by the Steelers, who held Johnson to 34 yards on 16 carries. Johnson went on to gain 125 the following week against the New York Giants in what would've been the record-tying game.
Johnson was named to his third Pro Bowl after last season, so he held out for more money and missed this year's training camp. He got off to a slow start, but his 101 yards rushing last week against Cleveland gave him 199 (2.9 avg) yards in four games.
There's little doubt he'd like to keep his momentum rolling today against a defense he's yet to crack, but one that's been cracking against everyone else this season.
"They're going to run the ball the whole time, based on last week," Steelers defensive end Brett Keisel said of a unit that was shredded for 180 rushing yards by Houston.
"That was our main focus out there (in practice this week). I think we only had like four or five pass plays (Thursday) and most of the rest was run. We think they're going to give us a heavy dose."
The Steelers' run defense is allowing an unheard of 4.8 yards per carry (franchise record-high is 5.0 in 1934). Yet, the Titans are averaging only 2.8 yards per carry (franchise record-low is 3.1 in 1971).
"You will see two scalded groups playing on Sunday," was how Tomlin summed up the game's primary matchup.
Larry Foote will step in at inside linebacker and force Lawrence Timmons outside in place of Harrison. Chris Hoke and Steve McLendon will rotate in Hampton's nose tackle spot. Ziggy Hood will replace Smith at left defensive end.
With first-year coach Mike Munchak and free-agent quarterback Matt Hasselbeck debuting for the Titans, they lost their opener, but have since beaten Baltimore, Denver and Cleveland the last three weeks.
"Matt Hasselbeck has done an awesome job for these guys," said Tomlin. "He's done a very good job of taking care of the football. They've gotten yards in chunks. He's spreading the ball around to a variety of receivers."
The Titans will miss their best deep threat, Kenny Britt, who underwent surgery Friday on torn ACL and MCL. Former Steeler Nate Washington becomes the main target with second-year receiver Damian Williams stepping into the starting lineup.
Hasselbeck, who's engineered the Seattle Seahawks to only 10 points in his last two games against the Steelers, hopes to improve upon his 104.7 passer rating this season against a team that ranks first in the NFL in pass defense, and a team that is, as Tomlin put it, "hacked off, and they should be."
Hines Ward provided a glimpse of what it means to be "hacked off."
"It's just shocking because we're usually the one out there setting the tempo," Ward said. "We shouldn't have to wait around for somebody to have to hit us in the mouth and wake us up before we start playing good football. We just need to be consistent from the first quarter through the fourth quarter. We need to be a consistent ball club, to physically impose our will on somebody, to keep coming at them, keep coming at them.
"There are a lot of prideful guys in here. We know we're not playing well. We've got a great team coming in, so it's going to be exciting."