Ranking the NFL's 50 best linemen, combining offense and defense: Aaron Donald, Watt brothers lead the way

Who are the NFL's best players in the trenches when you compare offense and defense? That's what we tried to figure out with the debut of our NFL lineman rankings.

At Pro Football Focus, we grade every player on every play in every game, which gives us a unique viewpoint on play in the trenches where the story isn't as easily told by readily available statistics like it is at other positions. Using PFF grades and statistics from previous seasons -- with extra weight given to results through the first four weeks of the 2020 season -- these are our top 50 offensive and defensive linemen right now.

We're including all edge defenders in this ranking, including players who line up primarily as outside linebackers. We're not including players who are out for the season, however, with apologies to injured stars Nick Bosa, Von Miller and Brandon Brooks.

The final results ended with 27 offensive lineman and 23 defensive linemen. Leading the way for the positions were the offensive tackles (14), followed by the defensive tackles (11). Let's start with the clear choice at No. 1 overall:

1. Aaron Donald, DT, Los Angeles Rams

2020 grade: 87.7

Why he's ranked here: There isn't a player in the NFL who towers over his peers in the same way Donald does. Since entering the league in 2014, he has recorded a PFF grade above 90.0 in 37 regular-season games. The next closest interior defensive lineman in that span has done so in ... nine. Donald is a game-wrecker in its purest form.

2. Quenton Nelson, G, Indianapolis Colts

2020 grade: 72.0

Why he's ranked here: No interior offensive lineman has been more valuable to his team than Nelson has over the past two full seasons. The 2018 sixth overall pick has graded above 70.0 in 23 of his 36 regular-season games so far, and he has allowed just eight combined sacks and QB hits across 1,376 snaps in pass protection.

3. T.J. Watt, OLB, Pittsburgh Steelers

2020 grade: 93.8

Why he's ranked here: Watt has earned a 92.6 PFF grade since the start of the 2019 season, two points more than any other edge defender over that span, and he has started 2020 with three consecutive game grades above 90.0. Through four weeks of the season, no edge defender has a higher pass rush win rate than Watt's mark of 29.3%. His older brother J.J. was once considered the best edge defender in the NFL, but now it looks like it's T.J.'s time.

4. Khalil Mack, OLB, Chicago Bears

2020 grade: 92.1

Why he's ranked here: Mack finished the 2019 season with the lowest PFF grade of his career to date -- an 86.2, which ranked 13th at the position. That tells you all you need to know about the edge rusher, who has recorded at least 50 total QB pressures in all seven years of his career and already has 22 pressures and a 90.7 pass-rushing grade through four weeks of the 2020 campaign.