As we pass the midway mark on the 2018 NFL season, the Total QBR leaderboard is a good place to see which quarterbacks have dominated and which have struggled mightily through the first half.
While QBs most often are judged by wins and losses or touchdowns and interceptions, we like to rank them by the stat that measures their per-play contribution to their team's cause.
An explainer of QBR can be found here, but the main idea is to capture more elements of a quarterback's play than traditional methods consider. QBR includes the value (or lack thereof) of quarterback rushing, sacks, fumbles, relevant penalties and -- crucially -- the down and distance of every play. QBR works on a 0-to-100 scale, with 50 roughly average and 75 about Pro Bowl-caliber.
Which quarterbacks were the best and worst in the first half?
Total QBR: 85.4
Mahomes will beat you, and he will beat you quickly.
No quarterback has a higher Total QBR on passes thrown two seconds or sooner after the snap this season than the Chiefs' electric second-year signal-caller. And over the past three weeks, he has completed 42 of 44 passes on those thrown in under 2.5 seconds (roughly NFL average).
Give credit to coach Andy Reid for helping set up his quarterback to make those quick throws; but those plays also require trust, timing and quick instincts from the quarterback, all of which Mahomes seems to possess early in his career.
Defenses can sit back on their heels and play coverage if they want to, but then they might never get to the former Texas Tech flamethrower. The Chiefs have the second-best pass block win rate (via NFL Next Gen Stats) in the league. No matter what, Mahomes is trouble.
Total QBR: 84.5
The Brees-to-Michael Thomas connection might be the most deadly combination in football right now. Thomas' completion percentage above expectation is plus-18 percent, much higher than any other receiver with at least 40 targets, according to NFL Next Gen Stats. These two connect on more passes than we could reasonably expect given the variety of factors that the metric includes, such as air yards and defender positioning.
Brees also leads all passers in completion percentage above expectation, so the veteran signal-caller deserves a good chunk of the credit.
Total QBR: 76.6
FitzMagic might not possess Matthew Stafford's arm strength or Brees' accuracy, but he chucks it downfield like he has both. Frankly, it seems like he's got the right idea.
Fitzpatrick has attempted a higher percentage of his passes 20-plus yards downfield than every other quarterback in the league -- except teammate Jameis Winston. The difference? The veteran journeyman has the third-highest QBR on such passes while Winston is dead last. Whether Fitzpatrick can keep up that production remains to be seen, but at least to this point, he has lapped his competition in this area.
Total QBR: 30.8
Allen seems to have a weakness in dealing with pressure. Only C.J. Beathard has a worse QBR when under duress.
The good news is that the former Wyoming quarterback has an above-average pass-blocking group in front of him, according to our pass block win rate metrics from NFL Next Gen Stats. The bad news is that even with that support, he has been the least efficient quarterback in the league among qualifiers (no, teammate Nathan Peterman isn't qualified).
One look at the receiving corps suggests Allen isn't getting much help, but the early returns on a quarterback that entered the draft with plenty of questions have been poor. He has been out since Week 6 with an elbow injury but is on the mend.
Total QBR: 33.0
Give Darnold an A for accuracy on his self-assessment on Monday, when he said he was "just playing stupid." That line came a day after his four-interception performance en route to a Week 9 loss against the Miami Dolphins.
Darnold now leads the league in interceptions. His passes have not been as dead-on as his critique of his play, as the former USC Trojan has thrown off-target passes 21.7 percent of the time, the second-highest rate in the league.
Darnold has been notably poor on play-action passes and has the league's worst QBR on those plays. It's hard to know if that's a true weakness or just noise, but it's certainly something he and the Jets should evaluate.
Total QBR: 38.8
Simply put, Rosen has no time.
With the worst pass-blocking unit in the league in front of him, Rosen is forced to throw the ball quicker than his rookie colleagues and among the quickest in the NFL. However, that might be a sign for optimism for Rosen. With better teammates, the results could look significantly better.
But at the same time, he has not made the most of a bad situation. When Rosen throws quick and throws short, the results have been poor. He has the worst QBR on passes thrown before two seconds and those 10 or fewer yards downfield. In that way, he is the anti-Mahomes.