The 2016 NFL season is officially past its midpoint, which means it’s time to evaluate the best and worst performances of the first half. Today, ESPN Stats & Information will take a look at the best and worst QBs in the first half through the prism of ESPN's Total Quarterback Rating (QBR).

Top 3

Tom Brady: 91.3 Total QBR

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Since returning from his four-game suspension, Brady has been nothing short of spectacular. Through four games, Brady has a 91.3 Total QBR (on a 0-to-100 scale) and has had the highest QBR in the league in three of the four weeks he was in action. For reference, a season-long QBR of 75 is considered Pro Bowl level, and no player has completed a season with a QBR higher than 90.

What has made Brady so efficient this season? At 39 years-old, Brady is as accurate as ever. He leads the NFL with a 73.1 completion percentage and has yet to throw an interception in 134 attempts. That accuracy has translated to his deep ball, where Brady is completing a league-leading 63.6 percent (14-of-22) of his passes thrown at least 15 yards downfield, which is about 23 percentage points better than his average on those throws the last four years.

Honestly, we could pinpoint almost any area of the game (red zone, passing under pressure, sneaky efficient running) where Brady has excelled. One area worth noting, however, is his performance on third down. Brady has converted a first down on 31 of his 49 third-down action plays (63 percent), including a remarkable 52 percent of plays in which the Patriots had at least seven yards to go. Not surprisingly, Brady leads the league with a 99.7 QBR on third down and has added about 20 more points than an average QB would have on third down in his four games.

Dak Prescott: 83.8 Total QBR

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Precott has an 83.8 Total QBR through his first eight games, surpassing Colin Kaepernick (78.1) for the highest QBR by a player in his first eight career starts since we first started tracking this in 2006.

What sets Prescott apart is his impact in all phases of the game. He has added the second-most expected points with his legs and fifth-most through the air, the only player in the top five in both areas. Another key part of Prescott’s success is his ability to avoid mistakes, which is rare for a rookie. He has four turnovers and started his career with an NFL-record 176 pass attempts without an interception. Add in the fact that he has taken only 11 sacks, and only Drew Brees and Brady have a lower percentage of negative EPA plays this season.

Obviously the Cowboys’ offensive success is also a product of their elite offensive line and running game. But Total QBR tries to separate a QB’s impact from his teammates. Few QBs have been as productive and efficient as Prescott this season.

Matt Ryan: 82.3 Total QBR

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Ryan ranks third behind Brady and Prescott in Total QBR, which is a per-play efficiency stat. Once accounting for each player’s usage, however, no quarterback has had a greater overall impact than Ryan, who leads the league with 41 QB points added.

It should be no surprise to see Ryan near the top this list; the Falcons currently lead the NFL in yards per play, points per drive and offensive efficiency. The 2013 Broncos were the last team to lead the league in all three categories through nine weeks, and they went on to reach the Super Bowl behind MVP Peyton Manning.

Ryan has already thrown for a league-leading 2,980 yards and 23 touchdowns this season, the most by a Falcons QB through nine games in franchise history. Where have those yards come from? Ryan has been extremely accurate over the middle, completing 73.8 percent of his passes between the painted numbers for an NFL-high 1,831 yards and 15 touchdowns.

Bottom 3

Case Keenum: 39.7 Total QBR

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The award for the LEAST efficient QB in the league goes to Case Keenum. It’s worth noting, however, that QB play has not been awful this season; Keenum’s 39.7 Total QBR is currently on pace to be only the 24th-worst single-season rating since 2006.

Nonetheless, Keenum ranks last in the NFL in Total QBR and has been responsible for more turnovers (12) than touchdowns (10) this season. Most quarterbacks perform worse in losses, but 10 of his 12 turnovers have occurred in defeat, including eight such turnovers during the Rams’ current four-game losing streak. Overall, Keenum has cost his team about nine more points than an average QB would with the same number of plays. It’s no wonder that many are calling for head coach Jeff Fisher to turn to No. 1 overall pick Jared Goff going forward.

Ryan Fitzpatrick: 43.8 Total QBR

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Fitzpatrick has thrown a league-leading 13 interceptions this season, including five that came in the red zone. Those are game-changing plays that are largely weighing down some of his positive contributions throughout the season.

One area where there is no denying Fitzpatrick’s struggles is in the fourth quarter. He is completing an NFL-low 50 percent of his passes with one touchdown and nine interceptions in the final 15 minutes. Obviously the Jets were deploying a risker strategy to get back in the game in some of those situations, but Fitzpatrick has by far the worst fourth-quarter QBR (19.9) in the NFL.

The only reason Fitzpatrick doesn’t rank last in the Total QBR is through contributing with his legs and by drawing penalties. He ranks ninth in rushing EPA and third in penalty EPA, while contributing the fewest expected points through the air in the league. Fitzpatrick has now posted a QBR below 40 in four straight games, tied for the longest such streak of his career.

Ryan Tannehill: 44.5 Total QBR

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The good news for Tannehill is that he’s posted three-straight games with an above average QBR, which were not coincidentally all wins for the Dolphins. The bad news is he started so slow that he still ranks 30th out of 32 QBs in Total QBR.

Tannehill lives on the short passes with 52 percent of his attempts thrown within five yards of the line of scrimmage, the highest percentage of any QB in the league. As a result, he is one of four QBs that has gained more than half of his passing yards after the catch. Though Tannehill deserves credit for completing those passes, his teammates also deserve credit for turning those short attempts into long gains. One other factor contributing to Tannehill’s low QBR is the competition he has faced. No QB has faced an easier set of defense than Tannehill, whose unadjusted QBR fell by 4.5 points once accounting for the strength of his opponents.

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