World-class players double-fault; they do it all the time, just like us. You’d think they were way past the point of double-faulting but there are some very good reasons why it still happens, at all levels:

• The player hasn’t developed a reliable stroke.
  
• The player is fatigued from a long match.
  
• The player is distracted and has lost concentration.
  

I think double-faults are an important part of tennis.

They are a valuable test of a player’s mental make-up: A snapshot of what’s going on deep down inside during periods of high-tension and pressure.

How long can a competitor maintain his or her concentration before breaking down?

I think that all players have breaking points, but some break down sooner than others. Professionals and experienced competitors can hold up longer of course, but no one is superman.

Gary Sherby is tennis director at Racquets and Togs Tennis Center, 115 Bradford St., just off the downtown square. His tennis tips appear Sundays.