Sloane Stephens, the reigning US Open champion and world #3, thought she would have a tough day at the office having lost to Elise Mertens in straight sets last month at the Cincinnati Masters.

Mertens, from Belgium and just twenty-two years of age, is having an incredible season, winning three events including her second consecutive title at the Hobart International. She is currently ranked #15 having reached a career-high ranking of #14 in early August.  

Stephens served first and immediately faced pressure throwing in a double fault to go down break point. Despite facing four deuces and another break point, she managed to hold when Mertens’ forehand sailed long.

They remained on serve thru the next three games but in the fourth, the Belgian struggled with her ground-game and dropped serve when she donated a double fault on the fourth break point.

Stephens gave back the break as she too committed a string of unforced errors. Back on serve, both held to 15 in their next service games, but it was Stephens who finally took control of the set when she broke Mertens in the eighth game following an extraordinary cross-court forehand winner and crisp, stab volley winner on successive points.

Serving for the set at 5-3, Stephens continued to benefit from her opponent’s erratic play as the Belgian’s unforced errors continued to mount. Stephens closed out the set in forty-one minutes and was now a set away from the quarterfinals.

Mertens served first to open the second and immediately faced a break point. The Belgian’s ground-game clearly was off, as she was unable to consistently counter and redirect Stephens’ power. Despite hitting an ace, she threw in another double fault and was broken when she overcooked another forehand.

Stephens was unable, once again, to consolidate the break as she was broken in her first service game. Mertens unloaded on a monstrous forehand down the line to go up 0-30 and continued to play more aggressively as she broke serve with an exquisite backhand down the line and an inside-out forehand pass to level the set at one game apiece.

It appeared that the momentum had shifted as Mertens emphatically consolidated the break with well-executed groundstrokes off both sides. Stephens, under pressure, met the challenge as she held to 15.

They remained on serve thru six games. Mertens, serving at 3-3, could not dictate with the forehand as it continued to sail long or find the tape. Stephens seized the opportunity and moving forward, struck an outstanding forehand down the line to break and take the lead.

The American, now in total command, held to 15 and was just four points from the quarterfinals. Elise Mertens clearly did not bring her A game to Arthur Ashe Stadium. She faced break and match point when another backhand down the line went long.

Stephens clinched the set with a remarkable inside-out forehand winner. Although she won in straight sets, Stephens will have to significantly up the ante in the next round. Her level last evening will not win a second and consecutive US Open championship.

She committed 25 unforced errors to 17 winners and zero aces; that will not get it done against her next opponent, Anastasija Sevastova. The #19 seed is a crafty and versatile player more than capable of hanging with big hitters as she aptly demonstrated last year when she dispatched Maria Sharapova in the fourth round. This is her third consecutive appearance in the quarters and even though Stephens defeated her in straight sets last month at the Canadian Masters, it would be a mistake to underestimate the twenty-eight year old from Latvia.