Correlation doesn't always equal causation.

Connor Williams was forced to miss time after injuring his knee in the Dallas Cowboys loss to the Tennessee Titans.

Former second-round pick Xavier Su'a-Filo filled in for Williams, and Dallas' offense promptly took off, averaging 137.25 rushing yards per game, 224 passing yards per game and 23.25 points per game with Su'a-Filo in the lineup. When Williams started at guard the Cowboys averaged 125.88 rushing yards per game, 188 passing yards per game and 17.5 points per game. Moreover, the team is undefeated with Su'a-Filo as the starter and just 3-5 with Williams manning left guard.

Having said that, it's time for Williams to regain the starting left guard position, relegating Su'a-Filo to the reserve role he fits best.

Many of you are probably asking: Why mess with a good thing?

Because correlation doesn't always equal causation.

Su'a-Filo's appearance in the starting lineup is certainly correlated with an uptick in rushing production by the Cowboys offense; however, it would be foolish to believe that Su'a-Filo's presence on the starting offensive line is a main reason for Dallas' uptick in production. In fact, film review reveals that the Dallas offense has succeeded in spite of Su'a-Filo at times.

With that being said, let's take a look at a few reasons why Dallas would be wise to insert Williams back into the starting lineup.

Better in pass protection

The biggest reason why Williams should receive his starting job back is that he's much better in pass protection than Su'a-Filo.

On Williams' last 309 pass blocking snaps, he has allowed three sacks and 19 total pressures, meaning, on average, Williams allows a sack every 103 pass blocking snaps and one pressure per 16.3 pass blocking snaps.

On Su'a-Filo's last 155 pass blocking snaps, he has allowed four sacks and 11 total pressures, meaning, on average, Sua'-Filo allows a sack every 38.75 pass blocking snaps and one pressure per 14.1 pass blocking snaps.

Put simply, Su'a-Filo allows sacks and pressures at a more frequent rate than Williams.

Xavier Su'a-Filo gets done in by an impressive cross chop-club by David Onyemata, who timed and beat XSF's initial strike to get home for the sack. pic.twitter.com/RB7iV52gBE — John Owning (@JohnOwning) December 1, 2018

Su'a-Filo tends to struggle in pass protection on account of weight distribution issues and inaccurate hands.

Another sack given up by XSF. Holds up well initially, but fails to latch and control Onyemata, who is able to bully is way into a sack. pic.twitter.com/1f3Ym5Y3Ck — John Owning (@JohnOwning) November 30, 2018

On top of that, Su'a-Filo lacks variety with his strikes and struggles to re-leverage his hands when parried by a defender.

Despite his play strength, Su'a-Filo actually has a tough time anchoring against bull rushes because he lacks the lower-body flexibility necessary to drop his pad level and win the leverage battle. Su'a-Filo is constantly out leveraged at the point-of-attack in pass protection.

Because of his immense upper-body strength, Su'a-Filo is at his best in tight quarters when his hands can latch onto the frame of a rusher. However, when forced to play in space against defensive tackles who have any semblance of lateral quickness, Su'a-Filo struggles mightily. He lacks the foot speed, accuracy in his strikes and balance to consistently stymie the quicker interior defenders.

Xavier Su'a-Filo gets done in by an impressive cross chop-club by David Onyemata, who timed and beat XSF's initial strike to get home for the sack. pic.twitter.com/RB7iV52gBE — John Owning (@JohnOwning) December 1, 2018

On the other hand, Connor Williams is tailor-made to stymie the quicker interior defenders and has shown improvement in his ability to deal with power as the season has progressed.

Williams possesses the lateral mobility to mirror quicker interior defenders along with the accuracy in his strikes to latch onto their frame.

On top of that, Williams actually has a deep reservoir of hand techniques that he can use to stymie pass rushers, making it difficult for pass rushers to get into a rhythm against Williams.

This was an impressive rep from #DallasCowboys LG Connor Williams. After checking on Looney, Williams is able to bail out Tyron Smith, who was just beat by an inside swim move. The rookie is getting more comfortable. pic.twitter.com/w39kCLMlRi — John Owning (@JohnOwning) October 16, 2018

Moreover, Williams is more adept at 'finding work,' or helping his teammates, in pass protection. Despite being a rookie, Williams has done a nice job of staying on the same level as the rest of his offensive line counterparts, making it easier to identify and pass off stunts on top of handling blitzes.

Because Connor Williams lacks the core strength to anchor against the stronger DTs, he tends to try and lean on contact to compensate. Short counters that perfectly with a powerful arm-over move. #Cowboys pic.twitter.com/AQofTsIgmM — John Owning (@JohnOwning) September 10, 2018

Williams tends to struggle in pass protection when he's caught leaning at the point-of-attack. Because Williams still lacks from a play strength perspective, he has a tendency to lean, getting his weight over his toes, at the point-of-attack when defending power rushes to try an compensate for his lack of play strength; however, this leaves him ripe to be countered by more savvy pass rushers.

Still despite his struggles with power, Williams has proven to be vastly superior to Su'a-Filo in pass protection. He may lack the play strength Su'a-Filo has, but he's more technically refined with better movement skills and flexibility, allowing him to successfully stymie pass rushers with a higher frequency than Su'a-Filo.

More well-rounded run blocker

Even though the Cowboys running game has taken off with Su'a-Filo as the starter, that doesn't make him a better run blocker than Williams, who didn't receive enough praise for his efforts in the run game.

Now, as stated before, Su'a-Filo is much stronger than Williams, and his hulking 6-foot-4 and 310-pound frame allows him to smother defenders at the point-of-attack, especially on double teams and combination blocks.

Nevertheless, Su'a-Filo struggles in a lot of the other areas of run blocking. Su'a-Filo struggles with his aiming points in space, making him one of Dallas' least effective linemen when asked to pull block.

Xavier Su'a-Filo acquitted himself well against PHI, but this wasn't the best snap pic.twitter.com/xCehi10muy — John Owning (@JohnOwning) November 14, 2018

Su'a-Filo may possess elite play strength, but his stiff lower-body limits Su'a-Filo's ability to generate power at the point-of-attack, which is especially apparent when Su'a-Filo climbs to the second level to block linebackers.

On top of that, Su'a-Filo lacks the footspeed to be effective on outside zone concepts where he is forced to reach block a three-technique defensive tackle.

Even though Williams struggles to displace bigger interior defenders at the point-of-attack on account of his lack of play strength, Williams does well to move his feet and use his body to turn and wall off defenders.

Williams' best traits as a run blocker are his ability to block in space and climb to the second level. Williams' athletic ability allows him to thrive in space, and his ability to target and latch onto defenders at the second level of a defense and in space is rare for a rookie, which is why Williams thrives as a puller.

Moreover, Williams' footwork and athletic ability allow him to be more effective on outside zone concepts where Williams has to perform a reach block on a defender.

Even though Su'a-Filo's play strength allows him to be slightly more effective on double teams and down blocks, Williams is adept at a wider variety of techniques and blocks. It's closer than it was in pass protection, but Williams' versatility as a run blocker gives him an edge.

Health

On top of Williams being much better in pass protection and slightly better as a run blocker than Su'a-Filo, he's also the healthier player.

Su'a-Filo is currently dealing with a nagging ankle injury that forced him to be a limited participant in the practices prior to the Saints game.

Williams, on the other hand, looks totally healthy after his knee surgery earlier this season, evidenced by the fact that Williams was a full participant in each practice leading up to the Saints game.

Connor Williams only played in 2 snaps against NO, but he executed his assignment at a high level on each. It's time to put the rookie back in the starting lineup. #DallasCowboys pic.twitter.com/wxLUxpYq5B — John Owning (@JohnOwning) December 4, 2018

Williams actually received two snaps against New Orleans, and he executed his assignment (one against a linebacker and the other against one of the best defensive ends in the NFL, Cameron Jordan) at a high level on each, further proving that Williams is fine health-wise.

Final thoughts

Ultimately, the decision looks easy. Not only is Williams the more effective and well-rounded offensive lineman, but he's also healthier, younger and the Cowboys have more invested in him.

Now, some of the delay in sliding Williams into the starting lineup could be due to the change in offensive line coaches that occurred while he was injured.

With Marc Colombo taking over for Paul Alexander as the offensive line coach, the Cowboys have gone back to a blocking style more akin to when Bill Callahan and Frank Pollack ran the unit from 2012-17 - a time when Williams wasn't a part of the Cowboys roster.

Even though Su'a-Filo wasn't on the roster either, he has much more experience in variety of blocking schemes, as he had five different offensive line coaches (Paul Dunn and Mike Devlin in Houston, Keith Carter in Tennessee, and now Paul Alexander and Marc Colombo in Dallas) in his five years as a professional.

The only offensive line coach Williams had known in the NFL was Alexander, whose philosophy and techniques are vastly different than Colombo, Callahan or Pollack's. This could mean that Williams has needed some time to adjust to the new philosophy. However, even if that were the case, it's foolish to start a less healthy and talented player any longer. Williams has had ample time to get accustomed to Colombo's system, and it's time to give the rookie another shot.

Twitter: @JohnOwning