BRISBANE International Day 4 was filled with plenty of highs and lows, with the biggest news seeing world number one Ash Barty knocked out of the tournament.

Barty was on the back foot early, with American opponent Jennifer Brady far too good on the day with a great serve making for a great win – and ultimately the best of her career so far. Brady has been in stellar form with this her fifth win on the trot having played three rounds of qualifiers, causing plenty of errors from Barty in her opening singles match of 2020. The 4-6 6-7 victory will see Brady head into the quarter finals alongside three other Americans.

Fellow Australian, Ajla Tomljanovic went down in an enthralling three sets to second seed Karolina Pliskova, dropping the first set before making a comeback in the second. She used the last of her energy however, with Pliskova drawing on her experience to throw everything she had at the Aussie in the third set, running out 4-6 7-6 1-6.

Third seed Naomi Osaka prevailed in her match against Sofia Kenin, showcasing her work ethic and star power. It was a high intensity battle from the first serve with the opening set going to a tiebreak and ultimately falling the way of Kenin, but that is where her luck ended with Osaka kicking it up a gear to run out a convincing victor, 7-6 3-6 1-6.

Kiki Bertens continued her winning ways despite a slight dip in concentration in the second set, 6-3 2-6 7-5. She took control in the first dictating the play but was knocked off her feet in the second by Anett Kontaveit who displayed her heavy hitting and skills. But Bertens recovered, taking away the win in a hard fought third set.

Petra Kvitova made light work of Russian, Ludmilla Samsonova securing the win in straight sets. Statistically speaking it was a relatively even match when it came down to aces and points won off the first serve, but Kvitova was clinical on the second, winning 88 per cent of second serve points along with recording a maximum of 10 points in a row.