In baseball you can handicap how the starting pitchers tend to do in the later innings and the bullpens and how teams tend to do in the later innings of games. I understand that but I think it's too much of a crap shoot to cap because you never know if the starting pitchers will be around in the second half (it depends on pitch count and whether they're having a good game). Then, the pitchers that are used in the second half usually depend on the score. If a team is down 5 runs in the sixth you're almost definitely gonna get one of their weaker relievers but if it's a close game they'll send in one of their better relievers. I see too many variables in baseball to cap the second half of a game before the game starts.
As for basketball and football, the problem is similar. The result of the second half often depends on the result of the first half. For example, if a team is blowing out another team at halftime that usually means there will be significant garbage time with scrubs in the second half but there's usually no way to predict that before the game starts. There's all kinds of problems like that with handicapping the second half of these games before the game starts imho.
So, how do you handicap the second half of a game before the game starts?