Moments after Rafael Nadal booked his semi-final spot, David Law and Catherine Whitaker got together on The Tennis Podcast to review all the day’s action.Why was Nadal so emotional about reaching the semi-finals? How did he break down Tiafoe’s game so effectively? And will he have the same joy against Tsitsipas?As for Tsitsipas, how did he find a way past Bautista Agut? How significant is it that he’s now backed up the win over Federer? Was today’s victory actually even more impressive than that one? And how will his backhand stand up against Nadal’s topspin forehand?In the women’s draw, Petra Kvitova made light work of Ash Barty. Given the knife attack she suffered just over two years ago, are we guilty of taking her success for granted? Kvitova will face Danielle Collins in the last four. David and Catherine agree that Collins will probably divide opinion, but they explain why they firmly believe she's a good thing for tennis.Finally, David gets a nasty surprise mid-podcast.The Tennis Podcast will be produced daily throughout the Australian Open (and at all the Slams) after our Kickstarter was funded by our listeners. It is produced in association with The Telegraph. See acast.com/privacy for privacy and opt-out information.