The Difficulty of Defending Against the Semi-Bluff

To illustrate the difficulty of defending against the semi-bluff, we'll take a seven-card stud hand from our discussion of semi-bluffing in the preceding topic and reverse roles:
Suppose you bet on fourth street, and your opponent raises. Knowing your opponent is fully capable of semi-bluffing in this spot with something like a pair of 7s in the hole, you still should
probably not call with a pair of 9s. He may in fact have a pair of queens or jacks. Or he may be semi-bluffing with a four-flush. The problem is that your pair of 9s is no favorite over a four-flush with a jack and a queen. Thus, if your opponent has a pair of jacks, a pair of queens, or two pair, you may lose because he already has you beat; and if he has a four-flush, you may lose because he outdraws you (which with his over cards as well, he's a favorite to do). Even if your opponent has nothing better than a gut-shot straight draw, your two 9s with a king kicker are not a hand to be excited about. Consequently, even though you suspect this opponent is semi-bluffing, it doesn't do you much good to call with a poor hand because you have two ways of losing: You may lose to a legitimate hand or by being outdrawn.
Suppose you grit your teeth, close your eyes, and call your opponent's bet. on the table and deals the next card:
you to make a mistake, according to the Fundamental Theorem of Poker, in contrast to what you would have done if you could see your opponent's hand. Your opponent gained, and you lost. However, not knowing what your opponent had, you did make the only sensible play.)