In the latest edition of Game Set and Mats, Annabel Croft and the seven-time Grand Slam champion review day four of the Australian Open.
Juan Martin del Potro's exit was the big story from the men's draw and Mats argues that Del Potro's bigger body is not suited to the hot conditions. He also wonders whether the Argentine puts in as much work in preparation for the big events as the top players in the men's game.
On the women's side, Mats said that Maria Sharapova ignited the tournament with her victory but also said that the heat rules need clarification after Sharapova and opponent Karin Knapp were forced to play an epic final set in unfair conditions.
You hear Mats' thoughts in full, with match highlights, in the videos above.