Andy Murray admitted he considered pulling out of the Australian Open following his father-in-law's health scare.

Nigel Sears, the father of Murray's wife Kim and coach to Ana Ivanovic, collapsed while watching her match against Madison Keys on Saturday.

The British number one put his off-court concerns behind him to defeat Tomic 6-4 6-4 7-6 (7/4) at the Rod Laver Arena.

Speaking immediately after the victory Murray said: "Today when I woke up I felt quite drained, quite tired," Murray said.

"As the day went on and I decided to play, I started to focus a little bit better but definitely on the court tonight I was more emotional than normal.

"I was talking to myself after every single point almost from the first point through to the last, which was obviously not ideal.

"That uses up a lot of energy. Again, just that makes you sort of more kind of up and down throughout the match, as well.

"Certainly I was trying to just concentrate on the match when I was out there but like I said, it's been a hard, hard few days.

"Hopefully it gets better in the next few days. I just can't believe something like that happened a few days ago. It's shocking. Nige is an unbelievably fit guy. Very, very scary."

Murray will now play eighth seed David Ferrer for a place in the semi-finals, after the Spaniard had earlier knocked out John Isner in straight sets.

The Dunblane ace earned three breaks of serve to take the opening set and despite some inconsistency in patches, the 28-year-old doubled his advantage after an error from Tomic.

The world number two was rarely in any danger and closed out the match in a third-set tie break.