Tuesday, October 11, 2011
Why QBR favored Tebow over Rodgers
Tim Tebow did enough Sunday as a relief quarterback to convince Denver Broncos coach John Fox to make him the starting quarterback. The five drives Tebow led in the second half against the San Diego Chargers resulted in two touchdowns and a Total QBR of 83.2. Maintained over a full season, that level of rating would identify a quarterback as a “Pro Bowl candidate.”
Tebow’s rating was also slightly better Sunday than the 82.1 achieved by the Green Bay Packers Aaron Rodgers, who sliced up the Atlanta Falcons for 396 yards and two TDs. Some fans have asked how it was possible for Tebow to have the better rating.
• First and foremost, Total QBR is a rate statistic. It was designed this way so that it could be used to break down a QB’s performance over a season, a game, a specific set of plays, under certain conditions, etc. Tebow’s rating for Sunday represents his performance over 16 action plays, while Rodgers’ rating accounts for what he did over 47 action plays against the Falcons.
• Part of the Total QBR calculation is the “division of credit” aspect which divides up the team’s expected points added or lost on the play amongst the QB, offensive line, and receivers based on statistical analysis of 3 years of NFL video-tracked data. So while Rodgers did throw for 396 total yards on Sunday, the box score does not show that almost half of that total (197 yards) came via yards after catch. On the other hand, three of Tebow’s biggest plays came on the ground, including his 12-yard rushing TD to cut the deficit to one score. QBs are given significant credit for making plays with their feet in Total QBR, especially on scrambles, which Tebow had a couple of Sunday. Taking into account a QB’s rushing contributions is an advantage that Total QBR has over other rating systems that only look at a quarterback’s passing statistics.
• Total QBR is clutch-weighted, so the QB’s plays where the game was closest – whether those come in the beginning, middle, or end of the game – count more toward a QB’s single-game rating than the plays that occur when it was out of reach. In the case of Tebow, he came in with the Broncos trailing by 13 and struggled on his first couple of drives when the game was not that close (Broncos had less than 10 percent chance of winning on most of his first few plays). On Denver’s final three drives, he led the Broncos to two TDs and had them less than 30 yards from a game-winning score on the final play of the game. Those plays where the deficit was within one score count more towards his rating since they had a greater likelihood of affecting the eventual game outcome, and since he played well in that span, his overall rating for the game is quite high.
• Other than Tebow’s significant rushing (six carries for 38 yards) compared to Rodgers’ lack thereof (one rush for minus one yard), there are a couple other things that close the perceived gap between Tebow and Rodgers for this one game, or half-game, in Tebow’s case. Rodgers took four sacks for 27 yards while Tebow took none. In fact, Tebow had no negative yardage plays at all.
• Of Rodgers’ 44 combined passing and rushing plays, 14 went for first downs. Of Tebow’s 16 action plays, five went for first downs, giving the two QBs nearly identical first down rates. Again, if you look at things on a per-play basis, Rodgers and Tebow are much closer than it may appear at first glance. Remember, though, this was for a limited period and is not reflective of overall past performance for Tebow and probably does not predict future performance.
For exclusive video, stories and blogs about quarterbacks from every level of competition, check out ESPN's "Year of the Quarterback" page.