14:44 CET - That's a wrap on today's tennis, so be sure to keep an eye on our website for all the latest news, reports and roundups, and join us again tomorrow for another tracker covering all the semi-final and United Cup action!
14:38 CET - The last quarter-final in Hong Kong has ended prematurely, with Michael Mmoh retiring while 6-3, 1-0 down to fellow American Marcos Giron, who moves into the semis.
14:13 CET - Daniil Medvedev has won the final match of the day in Brisbane, coming from behind to beat Kamil Majchrzak 6-7, 6-3, 6-2 and complete the semi-final lineup.
13:21 CET - Poland have sealed their spot in the United Cup semi-finals after Katarzyna Kawa and Jan Zielinski beat Australia's Storm Hunter and John Patrick Smith in the decisive doubles rubber, 6-4, 6-0.
They'll now face USA for a place in Sunday's final.
12:38 CET - Second seed Alexander Bublik is safely through to the Hong Kong semi-finals after a convincing 6-1, 7-6(2) victory against China's Juncheng Shang.
He'll face either Marcos Giron or Michael Mmoh in the last four.
11:43 CET - Over in Brisbane, Marta Kostyuk has set up a semi-final date with Jessica Pegula after the Ukrainian secured an impressive 7-6(7), 6-3 win over sixth seed Mirra Andreeva.
11:39 CET - Alex de Minaur has drawn Australia level in their United Cup tie with Poland, with the men's world number six proving too strong for Hubert Hurkacz in a 6-4, 4-6, 6-4 triumph.
Follow the decisive doubles rubber here.
10:00 CET - Moving back over to Brisbane, Alex Michelsen has beaten fellow American Sebastian Korda 6-3, 7-6 in their quarter-final.
Three of the four semi-final berths are now sewn up in Queensland, and they are all occupied by Americans! The fourth won't be a Yank, however, Michelsean will face the winner of Daniil Medvedev and Kamil Majchrzak.
Meanwhile, in Hong Kong, Andrey Rublev has defeated Nuno Borges 6-3, 6-4 to set up a semi-final meeting with top seed Lorenzo Musetti.
09:08 CET - Iga Swiatek has given Poland the lead in their United Cup quarter-final tie with Australia after a 6-1, 6-1 dismantling of Maya Joint in just 58 minutes.
Meanwhile, in Auckland, top seed Elina Svitolina has come through an almighty battle to secure her spot in the semi-finals. The Ukrainian saw off Sonay Kartal in three sets, 6-4, 6-7(2), 7-6(5).
08:23 CET - Fourth seed Jessica Pegula is safely through to the semi-finals in Brisbane after a hard-fought 6-3, 7-6(3) triumph over Liudmila Samsonova.
Elsewhere, Lorenzo Musetti has progressed to the last four in Hong Kong, with the Italian beating home favourite Coleman Wong Chak-lam in straight sets, 6-4, 6-4.
07:30 CET - Good morning and welcome to our coverage of Friday's tennis!
There are a few notable results to catch you up on overnight, with women's top seed Aryna Sabalenka seeing off Madison Keys 6-3, 6-3 in Brisbane, while Karolina Muchova also moved into the last four after beating Elena Rybakina 6-2, 2-6, 6-4 in a topsy-turvy affair.
On the men's side of the tournament in Brisbane, Aleksandar Kovacevic has battled past Giovanni Mpetshi Perricard 7-6(3), 4-6, 6-3, while Alexandra Eala and Iva Jovic have advanced to the semi-finals in Auckland.
Check out the full schedule for tournaments in Brisbane (ATP), Brisbane (WTA), Auckland (WTA) and Hong Kong (ATP) via the links.