Serena Williams vs. Madison Keys: Score and Reaction from 2015 US Open

Serena Williams' pursuit of the calendar year Grand Slam and a fourth straight U.S. Open title rolled on in a 6-3, 6-3 fourth-round victory over Madison Keys on Sunday at Flushing Meadows.

A powerful serve allowed Keys to hang tough and at least apply some pressure on Williams, but the prohibitive tournament favorite was simply too much for her American compatriot.

ESPN Stats & Info noted how little time it took for Williams to secure her latest win—though it wasn't a true indicator of how well Keys played:    

Keys double-faulted twice to fall behind 5-3 in the opening set, which was all Williams needed to gain the upper hand early. Williams had only three unforced errors in the opening set and played perhaps her best tennis of the entire tournament in that stretch despite surrendering three games.

U.S. Open Tennis highlighted how Williams had little trouble in her own service games to start:

Tennis journalist Carole Bouchard alluded to how Keys couldn't expect to slug it out with Williams and ultimately prevail:

The first game of the second set saw Williams push Keys to deuce before the latter held with an ace on the ad in point. Keys fell into a 15-40 hole at 1-1, hit a second-serve ace and held once more in an impressive display of resilience.

Although Keys managed to shorten a number of points with her velocity and hit more first serves in play in the second set, Williams eventually broke to go up 4-3 on serve. All Williams needed from there was two more holds, and she did one better in breaking Keys once more for good measure. The match ended on another Keys double-fault—her sixth of the day.

Ben Rothenberg of the New York Times weighed in on Williams' performance:

Williams had 18 winners to a mere six unforced errors for the match, whereas Keys had stats of 24 and 19 in those respective categories. The blend of power and precision Williams displayed made her indefatigable even against an upstart budding star in Keys.

After Sunday's win, Williams spoke about the unique matchup that lies ahead, per tennis writer Erik Gudris:

Tuesday evening will mark quite a special occasion as Williams squares off with her sister, Venus, who cruised to victory on Sunday in only 50 minutes.  

The Williams sisters are hardly strangers in major tournament encounters, per ESPN Stats & Info:

Resurgent as her senior sibling is, Williams bounced back from a three-set match against Bethanie Mattek-Sands to dominate Keys, who didn't play badly at all.

Considering she is only 20 years old, Keys will be heard from again on the Grand Slam stage. Until Williams shows any signs of letting down, though, the rest of the players won't be able to muster much confidence. Williams doesn't even have to be at her best to beat anyone, and when she's on as she was Sunday, no one on the planet can defeat her.

Yet another U.S. Open triumph for Williams isn't inevitable per se, but she fortified her status as the prohibitive favorite entering the quarterfinals.   

Note: Stats courtesy of USOpen.org unless otherwise indicated.