In almost every match, one player is usually the favorite. Sometimes this is based on ranking and results and other times it is based on what they look like hitting the ball and the weapons that they possess.
If the player who is ranked lower or is perceived as being the weaker player, wins the match, it is considered an upset. I have always told the players that I coach, that being favored does not mean a whole lot. If the two players are remotely close in ability, skill in hitting the ball, and how they play a match, the better player will likely win most of the time. However, if the two players were to play 100 matches, I would bet on the player who is not as good winning quite a few times. In fact, tennis often comes down to how the players match up against each other. If one player has a great serve and the other player has a great return of serve, it may come down to how the server reacts if his great serves come back, and how the returner handles the opponent's best serves.
Also, tennis is different every time you step on the court. Every player has their good days and their bad days. Conditions can be a factor. There can also be crazy points that deflate one player and pump up the other. The point is: play every point the best you can. Always believe you have a chance to win the match. Never buy into the fact that the opponent is better than you or not as good as you. An upset is only a review of what someone thought would happen with the outcome. It is far from a 100% likelihood that the better player will win.
Take a look at the results on the ATP and WTA tours. It is rare that a player dominates each week and even wins the majority of the tournaments. Novak Djokovic, Ash Barty, and the best players cannot do it match in and match out and week to week. Use this idea to help beat a better opponent and be wary of this when you are the "favorite" in the match.
Steve Annacone, USPTA Elite Pro, is the Director of Annacone Tennis (http://www.annaconetennis.com) and MyHamptonsPro based in Sag Harbor, NY (http://www. myhamptonspro.com) and Tennis Professional at Ventana Canyon Golf and Racquet Club in Tucson, AZ. For details on lessons, clinics, or coaching, contact Steve at firstname.lastname@example.org or call 865-300-7323