After 13 weeks of the NFL season, one of the continued trends is the impact of offensive lines on the league’s landscape. Teams like Minnesota and Seattle appear to be severely hampered by the lack of quality they have up front, while in Dallas, the performance of the starting five gives the Cowboys a foundation on which to become the league’s best team, despite a rookie at both quarterback and running back.

There may be a shortage of quality linemen throughout the league, but there remains a lot of impressive individual performers this season. Here are the top 25 NFL offensive linemen entering Week 14 of the season.

[Editor's note: This list was compiled based on Pro Football Focus' player grades, but does not stick to them 100 percent; subjective adjustments have been made by Senior Analyst Sam Monson for scheme or role variances between the players. This list was originally published on Wednesday, Dec. 7, prior to the Raiders-Chiefs Week 14 Thursday night game.]

1. Trent Williams, LT, Washington Redskins (91.5)

Returning in Week 14 after serving a four-game suspension, Trent Williams has been the best lineman in the league when on the field this season. The Redskins LT has allowed just 10 total QB pressures across the eight games he has played, and has even had to moonlight at guard in-game when injuries forced a reshuffle for Washington. Williams has been one of the league’s best run blockers, but has upped his game in pass protection and is playing the best football of his career, reminding people of his 2013 season, when he was arguably the league’s best tackle. It has taken him a few years, but Williams is finally repeating that performance over a full season (or full season minus four games).

2. Matt Paradis, C, Denver Broncos (91.0)

The development of Denver Broncos center Matt Paradis has been one of the stories of the season, albeit one that’s getting virtually no coverage. A year ago, Paradis was okay, but showed little to suggest that he would become the best center in the game in 2016. His highs were good, but three of his five best performances came in a three-game stretch featuring two bad defensive lines. This season, he has only really recorded one below-average game (against Atlanta), and has otherwise been excellent. Paradis has surrendered just eight total QB pressures, and been responsible for his quarterback hitting the turf just once.

3. Kelechi Osemele, LG, Oakland Raiders (89.1)

Kelechi Osemele cost Oakland big money this past offseason, but he is living up to the investment, and is a big reason why the Raiders' line has been as good as it has. Like Washington's Trent Williams, Osemele also had to do a little moonlighting mid-game, kicking out to left tackle for 24 snaps in Week 1 of the season, but at guard, he has been a force, allowing just seven total QB pressures in 12 games while also run blocking with impressive power.

4. Marshal Yanda, G, Baltimore Ravens (89.1)

Marshal Yanda has been the best guard in the game for a few seasons now, and though injuries have derailed his 2016 season slightly, he has still been right up there with the best. Injuries have forced multiple different line-ups up front for Baltimore, including keeping Yanda off the field at times, but in nine games this season, he has recorded full games at both guard positions and half of a game at right tackle for the Ravens. Across those games, he has yet to allow Joe Flacco to hit the ground, and has surrendered just five total QB pressures.

5. Andrew Whitworth, LT, Cincinnati Bengals (89.0)

Perpetually one of the league’s most consistent and reliable tackles, Andrew Whitworth has once again been the best lineman on the Cincinnati Bengals' roster, as well as one of the league’s best. Whitworth has surrendered four sacks, but only 13 total QB pressures this season, despite Andy Dalton holding onto the ball longer than he typically has in the past. Whitworth is getting up there in age (he turns 35 on Dec. 12), but that has yet to have a detrimental effect on his play.

6. David Bakhtiari, LT, Green Bay Packers (88.8)

When David Bakhtiari was handed his new contract by the Packers, it looked like a deal that was paying him for production he had yet to seriously threaten to achieve. Bakhtiari had been a solid pass blocker in the past, but never been able to consistently run block (definitely the right balance for that Green Bay offense). This season, however, he has taken a huge step forward to make that contract—at least for this year—look like money well spent. Bakhtiari has surrendered 14 total QB pressures, and has the league’s best pass-blocking efficiency score of 97.8, given how often the Packers throw the ball. When you factor in how long Aaron Rodgers likes to hold onto the ball, his performance has been even more impressive.

7. Donald Penn, LT, Oakland Raiders (88.1)

Donald Penn was thought to be on the decline when Tampa Bay let him go, but he is playing arguably the best football of his career, or at least the best since 2008. Penn is the only offensive tackle to start every game this season that has yet to surrender a sack. He has recorded seventh-best pass-blocking efficiency score (97.0), while also run blocking with the best players in the league at his position, dumping defenders on their backs with the power he brings to the field.

8. Alex Mack, C, Atlanta Falcons (88.5)

Another excellent free-agent acquisition, Alex Mack’s performance for the Falcons has been a major positive for a line that has been in need of improvement in recent years. Mack’s pass protection has only been okay—he has surrendered two sacks and 16 total pressures—a lot for a center—but his run blocking has been excellent. Mack has allowed Atlanta RB Devonta Freeman, in particular, to have big games by anchoring the middle of the line on run plays, securing blocks on the D-line before attacking linebackers at the second level.

9. Travis Frederick, C, Dallas Cowboys (88.5)

The man with the reputation as the best center in the game hasn’t quite reached that level this year, but he has been near the top all season long. Travis Frederick has surrendered just eight total QB pressures through Week 13 and has yet to surrender a sack. His performance in the run game against the Minnesota Vikings and Linval Joseph, in particular, was something to behold. Joseph is one of the league’s better run-defending defensive tackles, and Frederick easily handled him with his combination of mobility and technique.

10. Justin Pugh, LG, New York Giants (87.8)

Justin Pugh wasn’t a bad player at offensive tackle, but he has proven to be an excellent guard for the Giants. Pugh has allowed only nine total QB pressures and no sacks in the eight games he has played this season, and his run blocking has arguably been the stronger part of his game. The Giants have missed him in recent weeks, and been unable to get anything near the same level of play out of multiple different fill-ins at the same spot.

11. Joe Thomas, LT, Cleveland Browns (87.8)

For years, Joe Thomas was as good as a left tackle could be when it came to pass protection in the NFL, and while this season hasn’t been quite as incredible as years previous, he has still been a very good performer on the line for Cleveland. Thomas has surrendered 27 total QB pressures, but has been blocking for a succession of quarterbacks—none of whom do anything to help him out in terms of getting rid of the ball, or even remaining calmly in the pocket. Thomas has been excellent this season, but it's a slight drop on his previous untouchable standards. At his age (32 years old), the question of decline may be looming.

12. Zack Martin, RG, Dallas Cowboys (88.2)

Another member of the formidable Dallas offensive line, Zack Martin has been vying with the best guards all season, and has allowed just 12 total QB pressures on the year, while run blocking as well as any guard in the game. RB Ezekiel Elliott isn’t just leading the league in rushing, but in yards before contact (540), and much of that heavy lifting is done by Martin. His combination of speed and strength makes him a perfect fit for those zone-blocking plays Dallas loves to run.

13. Tyron Smith, LT, Dallas Cowboys (87.1)

At his best, Tyron Smith has the ability to be the best tackle in the game, but we haven’t seen that player consistently this season, and he has missed time due to injury. Despite all that, Smith has still been one of the NFL's best linemen, and gives Dallas a third member of its line among the best 15 linemen in the league this season (Frederick at No. 9, Martin at No. 12). Smith has surrendered 12 total QB pressures across the 10 games he has played, and run blocked well against some very tough competition.

14. Jack Conklin, RT, Tennessee Titans (87.5)

Jack Conklin has been a revelation as a rookie. A player that was expected by many to struggle badly in pass protection, the former Michigan State Spartan has been excellent in that regard, even if the Titans do help him out more than the best tackles in the game. Conklin has surrendered just 21 total QB pressures and been flagged only twice for penalties this season, while demonstrating the kind of run-blocking power that was his signature in college. Conklin’s play has been excellent outside of one rough game against fellow rookie Joey Bosa and the San Diego Chargers.

15. Rodney Hudson, C, Oakland Raiders (87.1)

While every franchise wants to build through the draft, the Oakland Raiders are proving that a team can assemble a top offensive line through free agency; while all three of the Cowboys' linemen so far on this list were drafted by Dallas, all three of the Raiders' to make it (Osemele at No. 3, Penn at No. 7) came via free agency. Rodney Hudson has yet to allow QB Derek Carr to hit the turf, and has surrendered only eight hurries all season, providing an excellent wall in the middle of that Raiders' line.

16. Brandon Linder, C, Jacksonville Jaguars (87.0)

There is very little to be cheery about on the Jacksonville roster, especially on the offensive side of the ball, but the team’s best player this season has been center Brandon Linder. Linder has allowed 12 total QB pressures, despite pass blocking for almost 500 snaps. He's been flagged just twice, and has the league’s fourth-best run-blocking grade at the position, with a mark of 83.9.

17. Taylor Lewan, LT, Tennessee Titans (86.8)

At the beginning of the season, Taylor Lewan was playing like the best tackle in the game; while his play has fallen off since then, he remains on solid footing, and is having by far the best season of his career. Lewan has allowed just one sack or hit all year, and 16 total QB pressures across 12 games. His run blocking was monstrous early in the season, but he hasn’t hit that level in the past month. Lewan's biggest issue is penalties, with 12 of them now to his name entering Week 14.

18. Zach Strief, RT, New Orleans Saints (86.1)

Right tackles have been outperformed by their left-sided teammates, despite (or because of?) some of the league’s most dominant pass-rushers coming from their side of the line. Zach Strief has gone up against some of the league's best edge defenders this season, and allowed 19 total QB pressures, with just three penalties to his name; he has earned good grades in all facets of the game.

19. Bryan Bulaga, RT, Green Bay Packers (85.9)

Bryan Bulaga is another player that has been somewhat one-dimensional this season for the Packers—nevertheless, he's excelled in the correct dimension for his team, grading extremely well as a pass protector and struggling a little in the run game. Bulaga has coughed up 22 total pressures and has the league’s ninth-best pass-blocking efficiency score, at 96.8. Not all pressure is created equal, though, and much of that pressure has come late in the play, and could have been avoided if the Packers' passing offense was in better rhythm overall; it's often pressure that other tackles wouldn't have even had a chance to surrender, because the ball would have more than likely been out.

20. David DeCastro, RG, Pittsburgh Steelers (86.3)

Former first-round pick David DeCastro is having the best season of his career, and may be close to realizing his potential as one of the league’s better guards, rather than merely a good one. DeCastro has surrendered three sacks and 17 total QB pressures this season, but his run blocking for the team has been very good, and one of the big reasons the Steelers have been able to have such success on the ground.

21. Josh Sitton, LG, Chicago Bears (86.2)

It’s still somewhat unbelievable that the Bears had Josh Sitton land in their laps unexpectedly just before the season after the Packers cut him loose in favor of cheaper, younger options. Sitton has been the league’s best pass-blocking guard for a few years, and though he hasn’t quite been that good for Chicago, he has been one of the league’s better guards overall, and allowed just five total QB pressures in nine games for the team. This represents one of the best and most fortuitous pickups of the offseason.

22. T.J. Lang, RG, Green Bay Packers (83.3)

Josh Sitton’s old teammate, T.J. Lang, has continued where he left off a year ago with another fine season. Lang has matched Sitton, allowing just five total QB pressures in nine games, and has yet to allow either a sack or hit on Aaron Rodgers. His run blocking hasn’t been as good as it was a year ago, though, which is a trend with most of the Packers' line, and part of the reason the team is so quick to abandon the run game.

23. Kevin Zeitler, RG, Cincinnati Bengals (85.7)

Cincinnati’s offensive line has had its issues this year, but those issues are coming from specific players along the line, and not the unit as a whole. Kevin Zeitler is having another good season, giving him a remarkably-consistent run of solid play dating back at least three seasons now. Zeitler has only been responsible for a single sack, and has allowed 14 total QB pressures for the Bengals this season while run blocking well and opening up holes for the RBs.

24. Ramon Foster, LG, Pittsburgh Steelers (85.1)

Ramon Foster's appearance here gives the Steelers a pair of guards on this list entering Week 14 (DeCastro at No. 20). Foster has earned good grades in both run blocking and pass protection, and has yet to allow a sack on the Steelers QBs this season. He has also (unusually) not been flagged once for a penalty, and has played more games than any other guard with that distinction by three clear games.

25. Brandon Brooks, RG, Philadelphia Eagles (84.6)

Another free-agent acquisition, Brandon Brooks has made a positive impact for the Eagles, even if the offense continues to decline as the season wears on. Brooks has been a well-balanced boost to the Philadelphia interior, and has solid grades in both run blocking and pass protection. He has allowed just 15 total QB pressures on the season, and been flagged only three times.