# Quarterbacking and The Positive Impact Factor

I'm finally back at it after life got in the way for a couple of weeks.
In breaking down potential NFL QB draft picks, experts will look at seemingly everything relevant and some things not so relevant. In rethinking where the fifteen QB's selected in the draft were taken, I unveiled the Total Percentage of Passes as Interceptions (TPPI™) stat. Strangely enough this is not emphasized in evaluating college QBs in the draft--INT percentage is an NFL stat. It is simple enough to calculate. You just take the number of INTs thrown and divide it by the total number of passes thrown. In trying to determine what the hype about Miami QB Jacory Harris is about, I calculated his TPPI but still wanted to dig deeper once I realized how high of a percentage his INTs was on his incomplete throws. Harris is also perceived to be a rushing threat, but the numbers don't pan out (his career average is almost negative 1 yard per rush). We all know that when a QB throws the ball that two out of the possible three outcomes are bad. Thus, what happens when the ball is released has to go into an impact factor. The ability or inability to run also makes a big difference for a QB in the college game and this too will go into the formula. The Positive Impact Factor™ is still in its initial stages of being thought out so I don't have an established benchmark. I decided to go with Colt McCoy (who actually was a dual threat) for the time being as he won more games at Texas (45-7 record as a starter) than any other QB in Division I history.
McCoy's TPPI is 2.7 (45 INT/1645 passes). He finished his career with 1571 rushing yards on 447 attempts. While this is only a 3.5 yard per carry average, these numbers include sack yardage lost. Sacks also count as attempts. McCoy completed 70.3% of his passes, so only 29.7% of the time he released the ball a negative play resulted. Obviously, sometimes an incomplete pass isn't so negative at all.
However, in looking at McCoy's 488 misfires over four seasons, the above play (and its championship implications) stands out as an anomaly. On 9.2% of his incompletions, McCoy threw an INT. As a contrast, former Troy QB Levi Brown, who was selected 124 spots behind McCoy in the draft threw an INT on only 5.1% of his incompletions. Brown's TPPI was a 2.0. Therefore, not all incompletions are equal impact wise. McCoy's rushing stats were a positive for Texas on average, besides the yards gained he also scored 20 rushing TDs. Brown finished with 24 yards gained for Troy and 1 rushing TD, so while his attempts were positive on average, their impact was clearly not equal to McCoy's for Texas.
You will notice that extremely negative plays count more than extremely positive plays. This is to allow a more level field of comparison between QBs playing in various systems. Former LSU QB Matt Flynn was not expected to throw the ball 40 times a game but was still highly successful for the Tigers. Flynn's TPPI was 3.0% with a 6.8% INT/incompletions, an extremely positive play factor of 6.2%, an extremely negative play factor of 6.8% (he had 0 fumbles total) and a Positive Impact Factor of 52.2. Now for the McCoy and Harris stats:
McCoy had 1645 passing attempts and 447 rushing attempts for 2092 touches. He had 132 total TDs to count for extremely positive plays which equals 6.3%. His negative plays equal: 488 incompletions, 28 fumbles, and 92 sacks taken for a total of 608 plays. The negative plays divided by the touches gives McCoy a baseline of 29.1% negative plays. McCoy's extremely negative plays were 9.2% INT/incompletion and 2.2% fumbles lost/attempt which add up to 11.4%. Dividing his extremely negative plays (45 INT, 10 fumbles lost) by total negative plays (608) and multiplying times 2 gives McCoy a 22.9 extremely negative play factor. Adding that factor to his negative play percentage results in a number of 52. McCoy's Positive Impact Factor is then a 54.3. How does Jacory Harris stack up?
Harris has accumulated 600 passing attempts, 93 rushing attempts and one reception for 694 touches. Harris has 39 total TDs for an extremely positive play factor of 5.6%. His negative plays equal: 240 incompletions, 11 fumbles and 45 sacks taken for a total of 296 plays. His negative play percentage is 42.7. Harris' extremely negative plays (10% INT/incompletion, 4.3% fumbles lost/attempt) add up to 14.3. His extremely negative play factor is 28.6, with his total negative number being 71.3. Therefore, Jacory Harris' Positive Impact Factor is 34.4. Despite his extremely positive play factor being double that of McCoy's, Harris also has a high extremely negative play factor which severely hurts his Positive Impact Factor. In other words, Harris is a high risk, not high enough reward QB at this stage in his career.