MADRID - Play returned to the Madrid Open on Tuesday, after a power blackout across Spain led to the postponement of many matches Monday afternoon and evening.

Monday's delays meant there was some imbalance in the men's competition, with matches in the round of 16 and the round of 32.

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There was an upset in the round of 16 when top seed Alexander Zverev of Germany was beaten by Francisco Cerundolo of Argentina 7-5, 6-3, while Jakub Mensik of the Czech Republic advanced to the quarterfinals with a 6-2, 6-3 win over Alexander Bublik of Kazakhstan.

In the round of 32, 11th seed Tommy Paul won 6-3, 3-6, 6-2 over Russian Karen Khachanov, while Paul's fellow American Frances Tiafoe had a 6-3, 6-3 straight-set win to reach the round of 16 at the expense of Alexandre Muller of France, and Gabriel Diallo of Canada fought back after losing the first set to beat Britain's Cameron Norrie 2-6, 6-4, 6-4 in two and a half hours.

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Greece's Stefanos Tsitsipas produced a minor surprise with the 17th seed winning 7-5, 7-6 (3) over 10th seed Lorenzo Musetti of Italy, while Australian Alex de Minaur beat Denis Shapovalov of Canada 6-2, 7-6 (3).

Jack Draper of Britain won the first set against Matteo Berrettini before the Italian was then forced to retire due to injury.

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In the women's competition, Iga Swiatek of Poland was forced to dig deep to reach the quarterfinals and needed three sets to beat 13th seed Diana Shnaider of Russia 6-0, 6-7 (3) 6-4.

Fifth seed Madison Keys of the United States had an easier time with a straight-set 6-2, 6-3 win over Croatia's 19th seed Donna Vekic.

Finally, top seed Aryna Sabalenka of Belarus beat Peyton Stearns 6-2, 6-4 in a match in which Sabalenka dealt with her rival's serve effectively.