Let me pitch in on this one, since I base my betting philosophy on scoping out bettable underlays.
There is only one definition of underlay that is useful AS A STARTING POINT for determining smart money action on a horse. That is: an underlay is a horse that is overbet in comparison to the morning line.
Determining that a horse is an underlay to your personalized odds line is almost useless as it distorts the baseline. Simply put, if you think a horse has a hole in its record and are correct about it, there is no reason to think anyone else sees OR DOESN\'T SEE what you see. In other words, you need some sort of firm baseline.
Since there are usually several underlays in every race, your main task is to determine which is bettable. Again, to put this simply, it is usually the horse that should NOT be overbet. That\'s hard to determine. It takes thousands of experiences to make good judgements. However, the payoffs on overbet horses can sometimes be exceptional and, for me, it\'s worth the exercise.
This is more of an art than a science (and it is totally useless in major races, where the pools are so large that betting action by a horse\'s connections is almost impossible to discern.) I have a dozen rules I use (a primary rule is to NEVER chase any overbet horse at 2-1 odds or lower), but I can tell you this is the best way I have found to cover 4 or 5 tracks at the same time and hit a high number of winners: about 1 in 3...never the favorite.
Before anyone chimes in to say how ridiculous this is, let me say two things:
First, I have absolute respect for Thorograph and for those of you who are experts in the Thorograph methodology. It is by far the best scientific approach there is to the subject.
Second, I have been in the business of breeding and racing horses and I came to base my betting on betting action because I know that 95% of the people in the business survive on it themselves. It behooves all of us to take their betting action seriously, because it is the basis of their livelihood. The only problem: it is NOT easy to read the board...once you learn how, however, it is profitable.
