Sabalenka ousts former doubles partner Mertens to reach Wimbledon quarter-finals

World No 1 forced to work hard for 6-4, 7-6 victory Siegemund next up after win over Solana Sierra Tennis players often say it's hard to play against a friend, the killer instinct never quite as easy to call on as it might be against someone else. Aryna Sabalenka, the world No 1, has rarely had that problem but she was pushed hard by her former doubles partner Elise Mertens before winning through 6-4, 7-6 (4) to reach the quarter-finals. Mertens had won just two sets in their past nine matches b...