Tennis players on the pro tour rarely step on the court feeling 100 percent physically. They almost always have nagging injuries, soreness, or sometimes even chronic problems that are basically caused by the repetitive nature of the game.
A player needs to pay attention to these issues and do everything possible to limit them, reduce the severity, and hopefully make it less likely they will reoccur. If the injury is likely to get worse, cause other injuries, or severely limit the player's ability to play close to their normal level, it may make sense to take some time off, or withdraw if you are playing a tournament.
Many injuries are manageable and if you are a good player, you may be able to structure your game so that the injury is not as evident. Shorten the points if necessary, hit more deep and down the middle shots to reduce the angles, and focus on the beginning of the point so the opponent is doing more of the running than you are.
One of the most amazing statistics in the modern game of tennis is that Roger Federer has never stopped playing a match once he starts it. He has been able to do this because his decision making (along with the help from his team) is very thoughtful and based on what I stated above. He doesn't put himself in a situation that will result in a default due to an injury.
Try to play whenever possible, but be aware of your body and stay off the court if you think you are risking further damage or feel strongly that you will not be able to compete at a level that gives you a chance to win the match due to your injury.
Steve Annacone, USPTA Elite Pro, is the Director of Annacone Tennis, www.annaconetennis.com and MyHamptonsPro, www.myhamptonspro.com throughout the Hamptons, NY. In addition, Steve and Miguel Coelho have introduced the JET (Junior Elite Tennis) program at the Tucson Jewish Community Center (Tucson, AZ) for high level players ages 8-18. Please contact Steve at firstname.lastname@example.org