Here are links to some very detailed research articles pertaining to fourth-quarter comebacks:
Guest Post: Quarterbacks and fourth quarter comebacks, Part I » Pro-football-reference.com blog » Blog Archive
Quarterbacks and fourth quarter comebacks, Part II » Pro-football-reference.com blog » Blog Archive
Quarterbacks and fourth quarter comebacks, Part III » Pro-football-reference.com blog » Blog Archive
Chronology of the Fourth Quarter Comebacks and Game-Winning Drives Records » Pro-football-reference.com blog » Blog Archive
Keep in mind that theses articles were written in 2009 and 2010, so numbers for Peyton and Brady have gone up considerably. Nevertheless, the author does point out that differences in these stats exist, depending on the precise definition of fourth-quarter comebacks. For the purposes of this study, he utilizes the following definition:
"For it to be a 4th quarter comeback win, you must:
Win the game (no ties or losses)
Take the field with a 1--8 pt deficit (1--7 prior to 1994) and score as an offense (no fumble return TD to win the game)
It does not have to be the final winning score (hence, that applies to the number of game-winning drives)."
Unfortunately, the author cautions that "Due to a semantics argument/hiccup/tie-up, no one is able to agree on a consensus definition of what a 4th quarter comeback or game-winning drive in the 4th quarter/overtime is." He also makes an important distinction between fourth-quarter comeback drives and game-winning drives:
"
There can be a difference between a comeback and game-winning (GW) drive: FOR IT TO BE A COMEBACK, THE OFFENSE MUST OVERCOME A DEFICIT. Trust me; the importance of that statement justifies the usage of the caps lock. Not all comebacks are GW drives, not all GW drives are comebacks. If you never trailed in the 4th quarter, but the game is tied and you lead a drive to win the game, that is a GW drive, not a comeback."
This researcher also agrees with BadJerry20 on the desirability of more precise statistical measurement of performance under these circumstances but warns of intrinsic limitations to the available data:
"The ideal 4th quarter comeback analysis would be to:
1. Identify the games where a comeback (from a 1--8 pt deficit) was possible: this gives you all successes and failures. Just telling me a QB has 10 comebacks does not mean a whole heck of a lot. But if you tell me he has 10 comebacks in 13 comeback opportunities, I can probably say hes doing a great job. If he has 10 comebacks in 30 opportunities, he might be someone only as good as Jon Kitna.
2. Identify the situation of the drive: time it started and ended, starting field position, number of timeouts, etc. Not all comebacks/drives are created equal. Its a lot harder to come back from a 4-8 pt deficit with 30 seconds and no timeouts than it is to start the 4th quarter on the 1-yard line, down by a point.
3. Collect the drive statistics: attempts, completions, yards, length and number of plays, etc. Just your usual QB statistics. Obviously going 8/8 for 80 yards and a TD beats going 1/5 for 8 yards to set up a long FG.
4. Create advanced statistics to better understand performance: average deficit, average yards to go, average time left, points per drive, percentage of 3-and-outs, turnover likelihood, blown saves, etc. Along with having the number of successes and failures, this would be the most useful part of comeback
analysis. This is how you can begin to answer whos really the biggest choker in the league.
Unfortunately you need solid play-by-play data here, so the number of seasons you can obtain this type of data is greatly limited."
Finally, since we have introduced Marino and, to a lesser degree, Elway into this discussion, this researcher specifically analyzes their records in part one of this series (
Guest Post: Quarterbacks and fourth quarter comebacks, Part I » Pro-football-reference.com blog » Blog Archive). This particular research project is not my personal crusade, so I will refrain from further discussion.