For those wary of betting preseason football here’s a question: When’s the only time coaches tell you what they’re going to do?

Right there is the key to betting preseason football. Bookmakers can be sitting ducks. Lines come out the beginning of the week and by the middle of the week previously untold player rotation and motivation angles become general knowledge.

While bookmakers love football, they don’t care for preseason. They can’t do much to prevent steam plays except adjust the numbers faster. Some sharp gamblers regard preseason as the best betting opportunity of the year.

There are others, though, who treat preseason very carefully. They’re leery of betting a game when the object isn’t necessarily to win but to evaluate players.

“It’s almost like betting on wrestling because the coach gives you a script,” one professional bettor said about preseason.

Coaches want to avoid overtime at all costs during preseason. They fear injuries. Just ask the Falcons and Jets about preseason injuries. So don’t be surprised when coaches go for two-point conversions instead of extra points at weird junctures. It also doesn’t hurt to practice two-point conversions since extra points are so automatic, John Carney not withstanding.

This lessens the value of the number 3. It increases the importance of 1 and 2, which aren’t key numbers during the season. So keep that in mind when deciding on a short underdog.

Patience also is required. Edges usually don’t come until Week 2 when coaching philosophies start kicking in. How are they preparing? This is the only time of year when they’re happy to tell you.

The ideal spot is discovering a matchup when one coach intends to play his starters a lot longer than the opposition. The 49ers’ Dennis Erickson is noted for this. Erickson happens to be 14-8 (63 percent) against the spread in preseason.

Motivation can play a huge part, especially with first-year coaches. Check out the secondaries, too. Because officials figure to tightly enforce the chuck rule during preseason. This could lead to higher scoring games.

Some teams like Pittsburgh are placing a bigger emphasis on blitzing. Teams who blitz a lot during preseason often do well because their opponents aren’t ready for it with backup linemen. It’s almost an unwritten rule among the NFL coaching fraternity not to blitz much during preseason. But some clubs need to practice it under game conditions. Usually the coach won’t want to try it on an opponent he’s going to play during the regular season, however, because it can give that opponent extra motivation.

The coach himself can be handicapped by how seriously he’s treated preseason games in the past. Bill Belichick, Bill Parcells and Jeff Fisher, for instance, have all covered 75 percent of the time during their past 16 preseason games. Mike Shanahan is 7-2 against the spread and Brian Billick 6-2 against the spread when getting points in preseason.