First, you want to know how much a pitcher is going to be used. Most pitchers these days aren't great, so pitching staffs are overworked.
If a pitcher has a live arm - basically meaning he hasn't been overused - a manager with a taxed bullpen is likely to try to get him to a higher pitch count. Unless he's Pedro, this presents a number of opportunities.
Should you consider the over? Should you consider the other side?
This is not as obvious a statistic as hits+walk/innings pitched ratios, or ERA in recent starts. But it has possibilities:
Always try to know how many pitches the starter threw in his last appearance, and how many he regularly throws. Then look at the team's recent bullpen use.
If it's set up that the bullpen needs rest and the starter can go, say, 90 pitches, he likely will be allowed to give up more runs than normal.
In a manager's eyes, sacrificing one game for a healthy bullpen is fair trade. In a gambler's eyes, the sacrifice is all that matters.