The longest tennis match in the sport's professional history was 11 hours and five minutes long. Yet the time John Isner and Nicolas Mahut actually spent playing tennis on that occasion, according to The Wall Street Journal's calculations, came to a little under two hours. Hmmm, those marathon matches now seem a little less impressive, right?

Having done a little number-crunching, The Journal found that the average "active" playing time during tennis matches clocks in at 17.5 percent of the official match time.

Case in point: Andy Murray's almost-three hour, second round match against Leonardo Mayer. "It lasted two hours and 41 minutes—three minutes shorter than the average men's singles match at last year's U.S. Open. Mayer and Murray actively played for 26 minutes and 29 seconds, or 16.4% of the time," The Journal reported.

That doesn't entirely make tennis a waste of time. The Journal does explain that although tennis's "active" action times look somewhat puny on paper, the sport still offers more action than baseball, which features only 18 minutes of action in a three-hour broadcast, and football, which offers only 11 minutes of play in a 185-minute broadcast. 

The majority of time spent is eaten up by timed changeovers (the commercial breaks) during odd-numbered service games (i.e., at scores like 2-1, 3-2, and 4-3) and the time spent after points—professional players, according to the official rules, have 25 seconds in between points to catch their breath. However, players don't really pay attention to that time limit, and chair umpires hardly enforce it. A rally could last 15 seconds — or less than one (if someone throws down an ace). Given that fact, the time between points can start to outnumber the time spent playing quite quickly. 

There's one thing that the time violators have in common: a majority of the players who violate these rules (there are always exceptions) employ defensive games that allow for longer rallies and, often, more exciting points (e.g. Nadal, Novak Djokovic, Andy Murray) — and perhaps that's why they need more time in between points.

Anyway, without further ado: here are the highest-ranked, worst time offenders on the circuit today: 

Rafael Nadal

Average Time Between Points: 30 seconds.

How He Kills the Time: Butt-picking. It's gross, but it seems like a ritual habit for the king of the French Open. 

But seriously, here is a side-by-side comparison of Federer and Nadal's time between points. Notice how Federer can complete about three points in the same amount of time that Nadal takes between two points. 

Novak Djokovic

Average Time Between Points: 33 seconds

How He Kills the Time: Djokovic, although much better than he used to be, has a reputation for being a notorious ball bouncer. That involves milking the clock on big points by bouncing the ball more times than usual before serving.

Juan Martin del Potro

Average Time Between Points: Unclocked. 

How He Kills The Time: Staring at the ground. Also, arguing about time warnings:

Maria Sharapova

Average Time Between Points: We feel bad for the poor soul who has to time this. 

How She Kills the Time: Clenching her left fist. Looking at strings. Not looking at opponents. Fixing hair. Skipping. Bouncing. Staring.