Serena Williams will face Agnieszka Radwanska in the semi-final at the BNP Paribas Open, while Novak Djokovic beat Feliciano Lpez in the mens draw

A dominant Serena Williams proved far too strong for Simona Halep, the defending champion, as the American eased into the semi-finals of the BNP Paribas Open with a 6-4, 6-3 victory on Wednesday.

The world number one has yet to drop a set in four matches in California, and Williams made a tricky opponent on paper look out of her depth in the quarter-final encounter. The 21-time grand slam champion blasted 28 winners to Haleps nine.

She also recorded seven aces, aptly closing out the match with an unreturnable serve down the middle, broke the Romanians serve four times and improved her head-to-head record to 7-1 against her fifth-seeded opponent.

A right knee injury forced Williams to withdraw from the event last year, when she ended a self-imposed 14-year absence at the tournament, giving Halep a walkover in their scheduled semi-final.

Halep ultimately defeated Jelena Jankovic to capture the crown but her defeat to Williams keeps the American on course for a first Indian Wells triumph since 2001.

The third seed, Agnieszka Radwanska, stands between Williams and a spot in the final, with the world number one expecting a tough challenge from the Pole.

(Radwanska) knows how to play in big stadiums and big matches, big games, Williams told reporters. Obviously she does everything so well, including running, and this is a good surface for her because its a slow surface. I think I expect there will be a lot of long rallies.

Radwanska booked her semi-final berth when she fought back from 5-2 down in the second set on the way to a 6-2, 7-6 (7-3) victory over the world number nine, Petra Kvitova.

The 27-year-old, who was a runner-up at the event two years ago, raced into a 4-0 lead in the tie-break before wrapping up victory after a little more than an hour and a half at the Indian Wells Tennis Garden.

I am just so happy to be in the semi-finals here, Radwanska, who will rise to number two in the next world rankings following the win, said. I have nothing to lose, will have a good rest and be ready for the semis.

Radwanska, who beat Jankovic in the previous round, breezed through the opening set against an error-prone Kvitova on a baking afternoon in the California desert.

Though the Czech produced much better form to open a three-game lead in the second, Radwanska clawed back the deficit before dominating the tie-break with the help of a few generous net cords. Novak Djokovic avenged his only loss of 2016 with a ruthless 6-3, 6-3 victory over Feliciano Lpez as the Serbian top seed eased into the quarter-finals.

An eye issue forced Djokovic to retire against his Spanish opponent at the Dubai Duty Free Championships last month but he had his sights set firmly on victory for their rematch in California.

The world number one needed just 66 minutes to prevail as he won 75% of his points on serve and broke Lpez three times.

I have respect for his game, which definitely made me very cautious of approaching this match and made me very determined to impose my game plan from the very beginning, Djokovic told reporters. I was very solid. I didnt allow him to come to the net too many times. It was a good performance.

Djokovic enjoyed his best performance of the tournament to date and next meets Jo-Wilfried Tsonga, who defeated Dominic Thiem 6-3, 6-2, as the defending champion seeks an unprecedented fifth title at Indian Wells.

Earlier in the day, the third seed Stan Wawrinka was sent packing in the fourth round and the Swiss was very nearly joined by Rafael Nadal, who pulled off a Houdini-like escape to reach the last eight.

Nadal, the fourth seed and three times a champion at Indian Wells, rallied from 5-2 down in the final set, saving a match point on the way, before battling past the 18-year-old German prospect Alexander Zverev 6-7 (10-8), 6-0, 7-5.

The power-hitting Zverev had been bidding to become the youngest quarter-finalist at the event since 1989 and led 40-30 when serving for the match in the ninth game but his nerve deserted him at the Indian Wells Tennis Garden.

This is painful right now, but it doesnt change anything about the process, Zverev said.

Nadal won the last five games of the deciding set to advance and was delighted with the fightback.

I am especially happy about the mentality on court, the fighting spirit during the whole match, believing that I can win a match during the whole time even in the tougher situations, Nadal said.

Wawrinka was ousted by David Goffin, who sealed a 6-3, 5-7, 7-6(5) victory when his Swiss opponent netted a forehand in a closely contested tie-break after a wildly fluctuating match that lasted nearly two-and-a-half hours.

It was only the second time in his career that Goffin had beaten a player ranked in the top 10 and it earned him a spot in the last eight of an ATP Masters 1000 event for the second time.

Also advancing to the last eight was Milos Raonic, who overpowered Tomas Berdych 6-4, 7-6(7).

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