Alcaraz topped the Red Group and will face Green Group runner-up Novak Djokovic in a mouth-watering semi-final.
Britain's Andy Murray won the Cincinnati Open on Sunday when his opponent in the final, Serbia's world number one Novak Djokovic, retired injured.
A big puff of pizzazz seeped out of the Cincinnati Open on Thursday as its top seed Caroline Wozniacki slipped out and star attraction Serena Williams quit the tournament, along with third seed Victoria Azarenka.
Former world number one Serena Williams has pulled out of the Cincinnati Open with a toe injury, tournament organisers said on Wednesday.
The Indo-Czech pair were defeated 6-7, 6-7 by second seeds Daniel Nestor and Zimonjic in the quarter-finals of the Cincinnati Masters.
France's Jo-Wilfried Tsonga suffered a surprise defeat to qualifier Alex Bogomolov while Spain's Rafa Nadal and world number one Novak Djokovic passed their second-round tests at the Cincinnati Open on Wednesday.
They demolished the USA-Russian pair of Lilia Osterloh and Anastasia Rodionova in straight sets 6-2, 6-3.
Mirza beat Lepchenko 6-2, 6-2 to reach the quarter-finals in Cincinnati for the third straight year.
Maria Sharapova will meet Kim Clijsters in the final of the Cincinnati Open on Sunday after the pair came through contrasting semi-final ties.
Ana Ivanovic will meet Kim Clijsters in the Cincinnati Open semi-finals after progressing along with Russian teenager Anastasia Pavlyuchenkova and Maria Sharapova on Friday.
Roger Federer survived a scratchy performance to beat Marcos Baghdatis 7-6, 7-5 to reach the quarter-finals.
The third seeded Indian ace easily beat Olga Govortsova of Belarus at the US $175,000 WTA Tier III event.
World number three Roger Federer cast aside bad memories to defeat Argentina's Juan Martin Del Potro 6-3,7-5 at the Cincinnati Open on Tuesday.
They now face eighth-seeded pair of Canada's Vasek Pospisil and local boy Jack Sock, whom they beat 6-1, 6-4 in Paris.
Sania Mirza was the only Indian left competing in the Western and Southern Open by reaching the semi-finals as Leander Paes and Rohan Bopanna were ousted from the men's doubles with their respective partners in Cincinnati.
World No 1 Rafa Nadal fell to Cyprus's Marco Baghdatis 6-4, 4-6, 6-4 in the quarter-finals of the Cincinnati Masters Friday as three of the top four seeds lost out.
Sania Mirza and Monica Niculescu stunned Wimbledon doubles champions Vania King and Yaroslava Shvedova to storm into the quarter-finals of the the Western and Southern Financial Group Women's Open in Cincinnati.
The third seeded Indian ace got the better of unseeded American Abigail Spears in her opening match of the WTA tournament.
India's campaign ended at the Cincinnati Masters tennis tournament after Sania Mirza and Cara Black went down to Anabel Medina Garrigues of Spain and Kazakhstan's Yaroslave Shvedova in their women's doubles second round match.
World No 1 Serena Williams won a tense battle of U.S. Open champions by beating Australia's Samantha Stosur 7-6(7), 7-6(7) on Wednesday to reach the third round of the Western and Southern Open in Cincinnati.
Top three seeds Roger Federer, Novak Djokovic and Andy Murray moved into the third round of the Cincinnati Open with relatively comfortable straight set victories on Wednesday.
China's Li Na defeated a battling Venus Williams 7-5, 3-6, 6-1 to reach the final of the Cincinnati Open on Saturday after an enthralling two-hour nine minutes encounter.
Rohan Bopanna and Florin Mergea saved a match-point before emerging winners, while Sania Mirza and Martin Hingis were also tested en route to the quarter-finals of the ATP/WTA Western and Southern Open, in Cincinnati, on Thursday.
Bidding for their second consecutive Masters title, Mahesh Bhupathi and Mark Knowles moved to the quarterfinals of the Cincinnati Masters after edging past Feliciano Lopez and Fernando Verdasco in a tough three setter.
Paes and his Czech partner Radek Stepanek beat Jerzy Janowicz and Lukasz Kubot while Bopanna and Edouard Roger-Vasselin got the better of Andreas Seppi and Mikhail Youzhny in second round matches.
Mahesh Bhupathi and Mark Knowles' six-match winning streak ended with their semi-final loss at the ATP Cincinnati Masters event at the hands of Wimbledon champions Daniel Nestor and Nenad Zimonjic. The fourth-seed Indo-Bahamian pair lost 4-6, 3-6 to the second seeded Canadian-Serbian combination in a little over an hour match of the US$3 million hard court event.
Sania Mirza and her Italian partner Francesca Schiavone crashed out of the doubles event of the US$ two million Cincinnati Open following a straight sets defeat against top seeds Cara Black and Liezel Huber. The unseeded Indo-Italian pair lost 4-6, 3-6 to the Zimbabwean-American combination in one hour and 14 minutes in the second round of the WTA event.
China's Li Na showed plenty of character as she fought back to beat German Angelique Kerber 1-6, 6-3, 6-1 and win the Cincinnati Open title on Sunday.
World No 1 Carlos Alcaraz fended off in-form American Tommy Paul to reach the Cincinnati Open quarter-finals on Thursday
The world's top four players will face off at the Cincinnati Masters on Saturday as Roger Federer, Andy Murray, Rafa Nadal and Novak Djokovic go head-to-head in two mouth watering semi-finals.
Leander Paes and Mahesh Bhupathi won their third title of the season and first at Cincinnati after 10 years, following a hard-fought win over Michael Llodra and Nenad Zimonjic in the final.
The Indian duo of Leander Paes and Mahesh Bhupathi will take on the winner of the match between Serbs Janko Tipsarevic-Viktor Troicki and the Spanish combo of Marc Lopez-Rafael Nadal in the second round of the ATP Western and Southern Open in Cincinnati.
An angry and frustrated Andy Roddick crashed out of the Cincinnati Open in the first round on Monday after suffering a three-set loss to 47th-ranked German Philipp Kohlschreiber.
Novak Djokovic beat Rafael Nadal 6-1, 7-5 on Saturday to reach the final of the Cincinnati Masters and bring the Spaniard's 32-match unbeaten streak to a halt. Serb Djokovic will meet Andy Murray in the final after the 21-year-old Briton overcame giant Croatian Ivo Karlovic in the day's other semi-final.
Sania Mirza failed to make the main draw of the WTA Premier event in Cincinnati after going down tamely to local wild card entrant Alexa Glatch in straight sets in the second and final round of the qualifiers.
Five times Cincinnati winner Roger Federer blunted Andy Murray's attempt at a comeback, while women's World No 1 Serena Williams roared to victory as they moved into the semi-finals at the Western & Southern Open on Friday.
World number 19 Moya battled past Argentine Juan Martin Del Potro 7-5 3-6 7-5 in their third-round match, while Hewitt, ranked 20, eased to a 6-3 6-3 win over Austrian Juergen Melzer.
Sizzling hot Andy Murray roared into his seventh successive final with a commanding victory over Canadian Milos Raonic at the Western & Southern Open in Cincinnati on Saturday.
Iga Swiatek used an outfit change to help her reset after a poor start and beat China's Zheng Qinwen.