The NFL playoffs have existed in their current form since 1990, when a 3rd wild card team was added in each conference, increasing the number of franchises with tickets to the post-season to 12. The divisional (2nd round) games have the reputation of being strong for the favorites, and indeed they are. Home favorite have gone 50-16 outright in the second round games since 1990, for an almost 76% win rate. This is not surprising, since the home favorites are coming off a bye, giving them an extra week to rest and prepare, while their opponents have generally had a hard-fought wild card game the previous week. (As an aside, there have been two divisional round home underdogs in that span, both won outright.)
But, as always, the pointspread is the great equalizer. The average spread in those 68 divisional playoff games was 6.9, and the favorites managed to cover only 53 % for a 35-31 record (excluding 2 pushes). Ignoring the two home underdogs, the home favorites were a profitable 35-29 (54.7%), beating the spread by an average of 3.3 points. Considering the typical underdog value inherent in NFL lines, this is actually quite a strong trend towards the favorites.
Some may say this trend is already widely enough known to have been built into the current lines. Looking at 3- and 5-year moving averages of divisional round pointspreads, the spreads increased dramatically in the years from 1990 to 1997, possible reflecting incorporation of this angle into the lines. However, a dramatic reversal between 1997 and 2002 brought lines back into the same range where they started in the early 90s (and where they remain today). Whether this is a natural correction to an overreaction in the marketplace or a reflection of greater parity in the NFL is hard to determine. If anything, parity seems to be at an all-time low this year suggesting that lines might actually be too low. Today's lines are more similar to those in the early 90s, even with the knowledge of the strong home field advantage and considering the perception that only 2 or 3 teams have a chance to win the Superbowl this year. This might suggest that the favorites are undervalued this year based on past results.
An interesting trend emerges if we look at the magnitude of the favorites in a given year. In seven seasons, the divisional round favorites were favored by an average of more than a touchdown. In these 7 seasons, the favorites went 17-8-1 ATS (68%). In the years where overall perception of the favorites was worse (the 10 seasons where the average spread in the divisional games was less than a touchdown), the favorites only went 18-21-9 ATS. The 7 seasons where the average spread was above a TD had the favorites outperforming other years by an average of 2 points, including the past 8 consecutive seasons. Of course, this week's playoff round has all four home teams favored by more than a TD, fitting squarely within this better subset for the favorites.
The historical value on the favorites in the divisional round is likely due to skewed public perception. Importantly, the underdogs in the divisional round have been on TV the week before. They probably looked good in the prior game, as they must have done something to manage to advance into the second round. If they were underdogs the previous week, the public perception of them may be even higher, as they pulled an "upset" last week and will tend to be overvalued. Meanwhile, the divisional round favorites have had a week off, and many of them have cruised through the end of the season, usually resting key players in Week 17, if not even earlier. They haven't played solid football in a few weeks, they haven't made highlight reels recently, and the public's memory is exceedingly short. Thus, it is easier to jump on the bandwagon of the "hot" wild-card team, coming off an emotional win, than it is to back the team that has been out of the spotlight for a few weeks and whose strengths are a distant memory.
An argument can be made that any analysis of NFL playoffs is meaningless - there are too few games to achieve statistical significance, and, of course, this is true. The flip side of the coin is that if you wait until the situation or angle is certain, it will already have been built into the lines and will be worthless from a wagering perspective. Gambling implies a level of risk, and sports handicapping is no different, especially in the ultra-competitive NFL where edges disappear quickly into the extremely efficient market. To gain an edge you often have to work with incomplete information, including angles that have not yet achieved statistical significance due to small sample size. In other words, to make money you have to be willing to take a chance. That's not to say these angles should be bet blindly, but the historical performance of favorites is something worth considering in the overall scheme of your handicapping for NFL divisional playoff weekend.
History tells us that the favorites hold the value this week, and I see no reason to buck that trend, as the lines don't seem to be incorporating this angle. The spreads seem generally in line with most "power ratings", for instance, Sagarin ratings (available in USA Today). And as if on cue, the sports media and internet forums have been abuzz about how the underdogs are good bets this week - a sure sign that something is amiss. In particular, the "soup du jour" for the public bettors seems to be the Giants and Seahawks. Early estimates have the public hitting all the underdogs fairly heavily except for San Diego. This is another indication that at least 3 of the 4 favorites this week might hold value.
Of course, the best plays for this weekend are likely to be the "basic strategy" teasers, taking the Colts, Packers, and Cowboys down to less than a field goal. Favorites have won at 73.5% during this round, and you are not giving up much by laying the "dead" numbers of 1 and 2. A 3 team teaser at +180 only needs each leg to hit at 71% to be profitable (two teams at -110 odds is a little sketchier, needing 72.4% to break even). Home favorites in the -7.5 to -8.5 range typically are profitable teaser candidates, and given the situational help, may be even more so this weekend. Of course, those who waited to act may have missed the teaser boat on the Colts, now at -9 at most shops. With the Colts seemingly the public "lock" of the week, bettors may be better served waiting for 10's to pop up and taking the underdog with a line that already looks to be inflated.
Tease: Dallas -1.5, Green Bay -1.5
San Diego +10 (if available)
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