CHARLESTON — The former US Open and Miami champion Sloane Stephens of the US struggled to get past Sara Sorribes Tormo of Spain 7-6, 7-6 after grueling two hours and 37 minutes in the second round of the Charleston Tennis Tournament.

The Spaniard had to dig deep in her games to stay on the positive side of the scoreboard, taking 12 points less than the American and facing 17 break chances, fending off 11 of those to reach both tie breaks where Stephens had the upper hand to kick off the campaign with a winning start.

Sara had the advantage in the opening seven games, scoring two breaks to forge a 5-2 lead and wasting a set point on the return in game nine. Stephens somehow stayed in touch, pulling breaks back at 2-5 and 4-5 to level the score at 5-5 and creating two set points on the return at 6-5.

Sorribes Tormo fended them off to set up a tie-break that Sloane won 7-4 after a backhand down the line winner. The second set lasted for almost an hour and a half and they traded eight breaks of serve in the first ten games, with Sloane wasting two match points on serve at 5-4.

Sara erased them to break back in the very last moment, reaching another tie break where she opened a 4-2 advantage before Stephens rattled off five straight points to race towards the finish line, sealing the deal with a service winner in the 11th point to book the place in the third round.

Unlike the top seed, the second-best player in the draw Kiki Bertens had an easy day at the office, toppling a qualifier Martina Trevisan 6-2, 6-1 in 59 minutes for the 15th win of the season.

The Dutch held the strings of the match firmly in her hands, losing 11 points in seven service games, suffering one break and controlling the pace of the encounter with a superb performance on the return, winning 63% of the points behind Trevisan's initial shot and earning six breaks from seven opportunities Bertens created.

Kiki grabbed the last four games of the opening set after a break she suffered in game four and never looked back, taking ten of the final 11 games to march towards the finish line and secure the place in the third round, happy with the way she played in the opener.

The 11th seed Danielle Collins needed 71 minutes to dismiss Madison Brengle 6-1, 6-3, getting broken twice and erasing that deficit with a rock-solid display on the return, taking 60% of the points and scoring six breaks from 12 opportunities.

A qualifier Kateryna Kozlova defeated Kristyna Pliskova 7-5, 6-4 in an hour and 25 minutes, taking half of the return points for five breaks and playing better in the closing stages of both sets to seal the deal without wasting too much time on the court.

The 16th seed Petra Martic overpowered the young American Amanda Anisimova 6-4, 2-6, 6-1 in an hour and 43 minutes despite six loose service games.

Mihaela Buzarnescu, Maria Sakkari and Andrea Petkovic scored the opening round wins to advance and we should get some interesting second-round encounters on Wednesday as well. — Agencies