Ellerbrock was taken to a deciding set by Mathewson, eventually coming through 6-3, 3-6, 6-1 to set up a quarter-final with third-seeded Dutchwoman Aniek van Koot, who received a bye as one of the top four ranked players.

High temperatures meant play was suspended for more than five hours at the Sydney Olympic Park Tennis Centre after Ellerbrock and Mathewson had completed their first two sets.

The match resumed amid windy conditions, but Mathewson, who won her first meeting with Ellerbrock in 2009, was unable to stay with the German in the third.  

Ellerbrock’s compatriot Katharina Kruger was also in action today as the world number nine crashed to a 7-5, 5-7, 1-6 defeat against world number eight Lucy Shuker of Great Britain.

Victory for Shuker, in the first match of the year between two players ranked in the world’s top 10, furthered her bid for back-to-back Super Series titles having triumphed at the USTA Wheelchair Championships in September.  

She now goes on to face fourth seed Diede De Groot of The Netherlands in the quarter-finals.

Also through to the last eight are Saki Takamuro and Manami Tanaka, both of whom prevailed in all-Japanese first-round matches.

Takamuro overcame Momoko Ohtani 7-5, 7-6 to earn a tie with defending champion Jiske Griffioen of The Netherlands, while Tanaka beat Shiori Funamizu  6-4, 6-0 to ensure a meeting with compatriot Yui Kamiji, the world number two and 2015 champion.

World number one and 2016 runner-up Gordon Reid started his men’s singles campaign with a comfortable 6-0, 6-1 victory over Australia’s Ben Weekes, who earlier beat Japan’s Haruya Mizukoshi 6-0, 6-0 in the first round.

Awaiting him in the quarter-finals is Japan's Takuya Miki, a 6-0, 6-0 victor over Australia's Henry De Cure. 

France’s Stéphane Houdet, who is a close second to Reid in the world rankings, registered a 6-0, 6-1 win over Japan’s Yohei Matsuda.

He next faces fellow countryman Nicolas Peifer after the defending champion opened with a 6-0, 6-3 win over Japan’s Yoshinobu Fujimoto.

Other notable winners today were third seed Joachim Gerard of Belgium and fourth seed Gustavo Fernandez of Argentina, with the former triumphing 6-3, 6-0 at the expense of Japan’s Satoshi Saida and the latter proving far too strong for Australia’s Keegan Oh-Chee in a 6-0, 6-0 success.

Fernandez will play seventh seed Maikel Scheffers of The Netherlands, a 6-0, 6-2 winner against Japan’s Kouhei Suzuki, for a place in the semi-finals.

Reigning NEC Masters champion Gerard takes on sixth seed Alfie Hewett of Britain, a 6-0, 6-0 victor against Japan’s Daisuke Arai.

The quad singles round-robin is due to begin tomorrow with world number one Dylan Alcott beginning his title defence in Sydney against fellow Australia Heath Davidson, his gold medal-winning quad doubles partner at the Rio 2016 Paralympic Games.

Rio 2016 silver and bronze medallists, Andy Lapthorne of Britain and David Wagner of the US, are also scheduled to go head-to-head.

The same four players will meet in the quad singles round-robin at the Australian Open later this month.