By Steve Keating
NEW YORK (Reuters) - Angelique Kerber won a battle of grand slam champions when the second seed powered her way into the quarter-finals of the U.S. Open on Sunday with a 6-3 7-5 win over Petra Kvitova.
By reaching the last eight Kerber has put herself in position to end Serena Williams' long reign as world number one.
Williams, bidding for a record seventh U.S. Open title, will now need to reach the final to have a chance of retaining top spot.
The fourth-round match had a definite grand slam pedigree to it with Kerber, the Australian Open champion, going against twice Wimbledon champion Kvitova but failed to deliver any major excitement.
To be fair, Kerber and 14th-seeded Kvitova were handed a tough act to follow with the capacity Arthur Ashe Stadium crowd left buzzing about Frenchman Lucas Pouille's upset win over Rafa Nadal in a five set thriller that had an hour earlier closed out the day session.
Kerber was in command from the start, winning all the big points on way to taking the opening set.
Kvitova, the Rio Olympic bronze medallist, offered more resistance in the second before meekly surrendering with a double fault on match point to gift Kerber a place in the quarter-finals.
Kerber's victory set up an intriguing last eight clash with Italy's Roberta Vinci, last year's surprise runner-up advancing with a 7-6(5) 6-2 win over Ukraine's Lesia Tsurenko.
(Editing by Andrew Both)