We are heading into Conference Championship weekend, and that leaves us with a chance to power rank the remaining units from the four teams still vying for Super Bowl LI.

(If you’re an avid PFF Podcast listener, you will have heard myself and Mike Renner discuss the topic on our review show this week, which you can find here.).

Here's how each team stacks up, by position group:

Quarterbacks

1. Aaron Rodgers

This might be the toughest call on the entire list. Right now, there is nobody playing at the level Rodgers is at. He is the best quarterback in the game in the playoffs, even if Tom Brady and Matt Ryan were better over the entirety of the regular season. Rodgers has such a unique skill set that I’m not even sure how you craft a game plan to defend him right now. If you let him out of the pocket, he can make throws no other QB in the game can – like the one that finally finished off the Dallas Cowboys last week, on third-and-long – but if you rush only to contain him in the pocket he just sits there behind the best pass protection in the league and picks you apart, anyway. The other QBs on this list may all be capable of beating you, but at least you enter a game with a firm plan to beat them. I’m not sure anyone even knows the best way of beating Rodgers the way he is playing right now.

2. Tom Brady

He earned the highest regular-season grade — 99.3 — PFF has ever given a QB, dating back to the 2006 season. He also has a very impressive postseason history, even if his game against Houston last week was far from his best.

3. Matt Ryan

He got the playoff monkey off his back against Seattle, and has had the best season of his career, but will he be able to out-duel Rodgers in what looks like it'll be a shootout this week?

4. Ben Roethlisberger

At his best, he can mix it with those above him on this list, but Roethlisberger has been inconsistent this season, throwing 11 picks from a clean pocket, compared to a combined 15 from the other three QBs.

Running backs

1. Pittsburgh Steelers

Le’Veon Bell is the Aaron Rodgers of running backs right now in terms of being near unplayable. Bell’s unique, patient style of setting up blockers and simply waiting for defenders to make a mistake in gap integrity makes him a very difficult back to bottle up, and combined with his burst, quickness and ability to make moves in an instant, it means he is guaranteed to rack up yardage.

Add to all of that his ability in the passing game as a receiver, and the Steelers have one of the best backfield weapons in the game at the peak of his powers heading into this weekend. While other teams have a committee that can do some of what Bell can, he is a one-man, star-studded backfield that has been carrying this Pittsburgh offense.

2. Atlanta Falcons

The combination of Devonta Freeman and Tevin Coleman has given Atlanta an extremely explosive backfield, both on the ground and through the air as receivers. Both runners are big-play threats any time they touch the ball, and together combined for 24 runs of 15 or more yards during the regular season — two more than any single back managed. Both players were top-10 players in breakaway percentage this season (percentage of yards coming on runs of 15 or more yards), and each has the same kind of ability after the catch in the passing game.

3. New England Patriots

The Patriots have an incredibly versatile backfield, with a sequence of diverse skill sets allowing their running game to take pretty much any form in a given game. They can go power-heavy with a player like LeGarrette Blount or use Dion Lewis as more of a scatback to adapt to whatever defense they face.

4. Green Bay Packers

As much as I like the ability and potential of Ty Montgomery at running back, the Packers simply don’t use him enough to be as confident about him as the backs from the other three teams. Montgomery led the league in yards after the catch per carry this season (5.1), but has fewer than 100 total carries this season including the playoffs.

Receiving corps

1. Atlanta Falcons

Julio Jones is arguably the best receiver in the game, and a matchup nightmare for defenses. What’s even more worrying for the Packers is that the Falcons are also very good at scheming him open, as well as just allowing him to go out there and beat his man. Behind him they have weapons out of the backfield, some solid play out of Taylor Gabriel and Mohamad Sanu in particular at receiver, and some capable receivers at the tight end position, especially if they get Austin Hooper back to full strength. Hooper had two of his best graded games of the season in recent weeks as he has worked his way back for the Falcons offense.

2. New England Patriots

There is no Antonio Brown on the Patriots' roster, but they do have a stable of reliable, effective receivers that Tom Brady can trust and work well with. Julian Edelman is now New England’s all-time leading receiver in terms of receptions in the postseason, and they have useful weapons at all positions within the offense, with Martellus Bennett at tight end and players like James White and Dion Lewis out of the backfield.

3. Pittsburgh Steelers

Antonio Brown is one of the game’s best receivers, but the weapons outside of him are not nearly as impressive, especially as long as Ladarius Green remains a non-factor at TE. Brown had 151 targets in the regular season, and no other Steelers WR had more than 65. Le’Veon Bell was the team’s second-most productive receiver this season.

4. Green Bay Packers

Jordy Nelson makes a big difference to this unit, but even if he plays he won't be near 100 percent, and we have already seen this season that a Nelson who is less than 100 percent isn't nearly the same weapon.

Offensive line

1. Pittsburgh Steelers

Pittsburgh finished the season ranked third in PFF’s offensive line rankings, but they are playing even better now than their average over the year. If those same rankings were based on current form there’s a good chance they would be the No. 1 line in the entire league, because their starting five simply has no weaknesses. Alejandro Villanueva had been the weak link in the chain, but at midseason this year something clicked for him and he has been one of the game’s better left tackles since. He has been caving people in on run plays lately, and allowed just one sack over the last 12 games. He was one of three Steelers linemen not to allow a single pressure against the Chiefs, and this unit can both pass block and run block extremely effectively.

2. Green Bay Packers

Green Bay has the game’s best pass-blocking line, and it’s not even particularly close to the next-best. Aaron Rodgers holds the ball longer than any QB not named Tyrod Taylor on average (3.03 seconds this season, including the playoffs), and yet the Packers' line has the game’s best pass-blocking efficiency score of 85.3, allowing fewer total pressures than 22 other teams despite playing an additional two playoff games than most.

3. New England Patriots

The return of long-time line coach Dante Scarnecchia might have been the single most impactful move of the offseason, and he has had a transformative effect on a unit that struggled badly a year ago. Right tackle Marcus Cannon became a second-team All-Pro this season under his tutelage, and right guard Shaq Mason has developed massively, too, combining to form maybe the league’s most potent double team in the run game.

4. Atlanta Falcons

Atlanta has a top-10 offensive line in the league, and ranking at the bottom of the four in this case is no cause for shame. The import of Alex Mack at center in free agency was a huge boost to this unit, which has been solid all season. Only right guard Chris Chester has been an issue, surrendering six sacks and 45 total pressures over the regular season, plus a sack and hit against Seattle last week.

Front seven

1. Green Bay Packers

As strong as the offensive lines remaining are, the defensive front sevens are correspondingly weak, leading to some interesting matchups and the potential for plenty of scoring on Sunday. Green Bay may have the best remaining, with Mike Daniels a genuinely disruptive force inside, and multiple players capable of getting consistent pressure on the outside. Nick Perry has taken huge strides this season, and ended the regular season with 46 total pressures — 18 more than his previous career-high. Julius Peppers remains a player who can still have an impact on games, even in the twilight of his career, and was a huge factor in the team's first two playoff games, particularly against the Giants (he earned a sack, hit, two hurries and two batted passes in that game).

2. Pittsburgh Steelers

Pittsburgh’s defensive front seven may be the most high-variance of any of the remaining units. If they all fire and play to the best of their ability, this is the best remaining unit, but they also have the potential to be the worst if the reverse happens. The fact that James Harrison – at 38 years of age – is still their best edge rusher and only consistent source of pressure is a major issue. And while inside linebackers Lawrence Timmons and Ryan Shazier have very good athleticism and playmaking ability, they are inconsistent and can be the cause of big plays going against the defense, too, especially in coverage, where they have a tendency to bite on the first thing they see.

3. New England Patriots

This might be the most underrated front seven left, and while there is no consistent source of impact pressure, every member of the unit is solid, especially against the run. Schematically, the Patriots are also good at generating pressure from a variety of spots along the front, and as a defense this season, six different players had 20-plus total pressures, with one more (DL Alan Branch) managing 17. This front can defend the run and will generate some pressure, but they don’t have any one player who strikes fear into the opposition.

4. Atlanta Falcons

Vic Beasley has generated a lot of sacks this season, but those numbers flatter him, especially when you dive into how the sacks came about, or who he beat to get them. In recent weeks, he has struggled, totaling 12 pressures in his last four games despite playing some extremely poor tackles in those outings. Outside of Beasley, there is little in the way of consistent pressure, and this front is the worst remaining at defending the run.

Secondary

1. New England Patriots

New England has comfortably the best remaining secondary, with a couple of All-Pro players in the shape of free safety Devin McCourty and cornerback Malcolm Butler. Butler can be beaten at times, but he also notched four interceptions and 12 pass breakups this season. Logan Ryan in the other starting spot has the league’s third-best run-stop percentage among cornerbacks, while Duron Harmon at the other safety spot is a solid player who simply doesn’t make many mistakes. The weakness in this secondary is in depth and sub packages, where players like Patrick Chung and Eric Rowe can be targeted and exploited, but the starting four is one of the best units in the game.

2. Pittsburgh Steelers

Pittsburgh’s secondary is improving as the season goes on, and the young players who were such liabilities early in the year develop and find their feet. First-round rookie cornerback Artie Burns was picked on early in the year, but against Kansas City he allowed just two catches for 13 yards and he has allowed 40 or fewer receiving yards in seven of his last nine games starting. Their other top corners William Gay and Ross Cockrell are both also good coverage defenders, and the issues in this secondary are at safety.

3. Atlanta Falcons

Losing cornerback Desmond Trufant was a big blow to this defense, and this is a unit whose cornerbacks can be exploited. Robert Alford allowed seven touchdowns over the regular season, and they haven't yet been able to replace Trufant’s play as the No. 1 corner. Rookie Keanu Neal has been a pleasant surprise at safety.

4. Green Bay Packers

The Packers secondary wasn’t great before they suffered an injury crisis, but it’s safe to say that didn’t help it. The play of their young cornerbacks Damarious Randall and Quinten Rollins in particular has been a huge disappointment, with the pair combining to surrender 15 touchdowns this year, compared to four last season.