Geno Atkins is in game-breaking mode.

The Bengals are back to No. 1 in NFL scoring defense after Sunday's 31-7 victory over the Rams, the fourth time in five games they've held foes to 10 points or less.

And one of the big reasons is Pro Bowl defensive tackle Geno Atkins, a guy defensive coordinator Paul Guenther says should be in the conversation for Defensive Player of the Year.

"Ask anybody on the offenses we play and he's the first guy they look at," Guenther said Monday. "They say, 'We better have a plan for this guy.' And he's done nothing not to be in the conversation."

Atkins' pass-rush is well documented and his sack Sunday made him the NFL leader among tackles with eight. But Guenther believes he showed his dominance in the run game that stuffed Rams running back Todd Gurley on 19 yards on just nine carries. While teams have stopped Gurley the past month by loading the box, Guenther said he never called a loaded box in the base defense.

"We went with a light box. Seven. And the guys did a great job in it," Guenther said of how Atkins frees him up to call a game. "You don't have to use eight-man fronts; you don't have to use a lot of blitzes. He frees up guys when he gets doubled . . . He's a force against the pass and a force against the run."

ROSTER MOVES:

With backup cornerback Chris Lewis-Harris nursing what is believed to be a broken rib, the Bengals added former Ravens cornerback Asa Jackson to the practice squad and cut offensive lineman Dan France to make room.

But the deal had already been in the hopper before Sunday's injury. Jackson said he was summoned by the Bengals last Wednesday for Monday's workout of other cornerbacks.

The 5-10, 183-pound Jackson is well-known to the Bengals as a fifth-round draft choice of Baltimore in 2012 that played in 18 games for the Ravens in between stints on the practice squad. He didn't play against the Bengals this season, but played in four other games and blocked a punt at Arizona and a point after attempt against San Diego. After 27 career tackles (three on special teams), the Ravens waived him 10 days ago.

He played nearly 70 percent of the snaps against the Bengals as a nickel corner in the 2014 opener when the Ravens were decimated in the secondary for the Bengals' 23-16 victory.  

"The Bengals have always been a hard-playing team that has demanded a lot of respect from those guys in Baltimore for sure," Jackson said upon his arrival Monday. "Competitive respect, but definitely respect. I'm looking forward to being a part of that. These guys have always played tough. They've especially played the Ravens tough and you hear every year about the amount of talent that this team has. It's exciting to be a part of that."

Ravens general manager Ozzie Newsome and one of his former coaches, Bengals head coach Marvin Lewis, have a similar view of defense. So Jackson should fit right in with the Cincinnati style.

"Aggressive. Playing really shutdown-type corner guys," Jackson said. "Real aggressive, real fundamentally sound guys that will go out there and tackle. Ball hawks and playmakers  and what you really look for in corners. These guys really play ball."

The Bengals had to make a tough call when they also Monday waived third-year linebacker Sean Porter from the physically unable to perform list. Porter, a fourth-round picked in 2013, had been medically cleared to resume practice and Tuesday marks the end of a 21-day window in which he was allowed to practice without counting against the roster limit.

Porter played just one pre-season game as a rookie before suffering a season-ending torn labrum the next week in practice. The next training camp he played in two pre-season games but injured his hamstring and didn't play in the first three games of the regular season. When made his NFL debut, he tore his ACL on the opening kickoff in New England.

BREAKING IT DOWN:

The beginning of a big defensive day:

Give an assist to Bengals head coach Marvin Lewis.

On Sunday the Bengals hijacked Gurley's historic season. The first rookie to rush for 125 yards or more in four straight games and whose 565 yards in his first four career starts are the most in the Super Bowl era, Gurley got drilled Sunday for 19 yards on nine carries.

Go back to the second snap of the game when Bengals safety George Iloka missed a tackle on wide receiver Tavon Austin on a flipped screen pass out on the numbers to set up a third-and-one.

"Coach Lewis was getting on me," Iloka said. "He was like, 'Shoot your gun.' I need to shoot my gun more often."

He didn't wait to pull the trigger. On the next play, Iloka came down hill immediately when he saw a pitch to Gurley wide right, roared in unblocked, and dumped him for a three-yard  loss.

"It was ironic," Iloka said. "I made a harder play and pointed right at (Lewis). 'That's what I'm talking about.' For me, that felt good.

"Any team, we go into the game thinking they're not going to get a lot of this or a lot of that."

Iloka took it out of the holster plenty after that. To go along with his tackle for a loss, he had an interception and a deflected pass that turned into safety Reggie Nelson's huge interception with 31 seconds left in the half at the Bengals 15.

PBS D: The Bengals remain a tough out at home. They're giving up just 15 points per game in six PBS games this season and only Chargers quarterback Philip Rivers has thrown for two touchdowns. That home passer rating computes to 79.1, but go back over the last 26 home games when the Bengals are 21-4-1 and it is 68.7. That's highlighted by 26 TDs against 39 interceptions, as well as 68 sacks.

THIRTY SOMETHING: The number 30 continues to be magic for the Green-Dalton Bengals running game. After they rolled up 140 yards on 31 rushes against the Rams, it marked the 20th straight game they've rushed at least 30 times and haven't lost. They're 19-0-1 with the tie coming last season against Carolina and overall since 2011 they're 35-3-1. The last time they lost with at least 30 rushes came in Baltimore on Nov. 10, 2013 when 120 yards on 31 carries weren't enough in a 17-10 overtime loss.

SNAP JUDGMENTS: The Bengals loaded up in big formations much of the day to muscle a good defense. Even before tight end Tyler Eifert got hurt in the middle of the third quarter, it looked like fullback Ryan Hewitt and rookie tight end Tyler Kroft were going to play above their season average. Hewitt, averaging 39 percent, took 66 percent of Sunday's snaps. Kroft, averaging 16 percent, took 39 percent. Big back Jeremy Hill was headed that way before he injured his ankle early in the fourth quarter and played 47 percent of the snaps compared to his average if 41.