Sports: The GOAT

Tennis, like most sports, has seen a lot of changes over the years. The racquets have changed - modern designs allow for incredible topspin to be generated on shots. The surfaces have changed - slowing down across the board to emphasize longer rallies. Even the rules have changed; the newfangled Hawk-Eye electronic challenge system now plays a key role in many matches.

Through all these changes, it's probably impossible to crown one tennis player as "The Greatest of All Time." Today's tennis, for instance, is marked by power baseliners, with almost no one playing serve-and-volley any more. You also have to be in top physical condition to scamper along the baseline for hours at a time, which puts a huge emphasis on fitness and conditioning.

On Sunday, the world's no. 1 and no. 2 tennis players, Rafael Nadal and Roger Federer, will be playing for the Australian Open championship, and perhaps greatness. For Nadal, it's a chance to get his first hardcourt Grand Slam and his sixth overall, to be mentioned along with stars like Agassi and McEnroe. For Federer, the stakes are much higher - he has a chance to tie Pete Sampras' all-time record of 14 Slams.

It's a race against time for Roger Federer, whose career is probably entering its twilight phase. He doesn't dominate like he used to, at least outside of the Grand Slam events. In a best-of-three-sets match, players can now sometimes find enough vulnerabilities in Federer's game to win. In a Grand Slam match (best-of-five), though, Federer can use his nearly unlimited arsenal of shots and his raw determination to win, overmatching his opponents with guile instead of power. On Sunday, Roger will need every bit of his magic if he wishes to defeat Nadal.