"[T]ennis has a number of elements in common with poker.
Poker is like tennis in that we have a good idea of how strong
our own games are, but during the course of a match, we have
only a partial understanding of the strength of our opponent.
Smart tennis players always try to appear strong and in control, no matter how insecure they may feel. Their objective is to convince you that you are going to lose.
In poker, we have pay money to see all the cards, and sometimes it's not worthwhile. Tennis is different: we pay to see additional cards using physical and mental effort rather than cash, and this is almost always worthwhile.
In tennis, it always pays to assume that your opponents are bluffing. No matter how tough they look, or how outclassed you feel, if you play out your best game plan with maximum physical and mental effort, you always have a chance to win."
-- Allen Fox, Ph.D., Psychologist, Author, Wimbledon Quarterfinalist, from Tennis Lessons from Poker, Tennis Magazine, Page 74, (July-Aug. 2016)