Venus Williams battled injury to progress to the third round of the Australian Open with a 6-7 (6-8) 6-0 6-4 victory over Czech Republic's Sandra Zahlavova.

The WTA fourth seed was in agony, screaming with pain after losing the first set tie-breaker. However, after immediate medical treatment, she returned with her right thigh heavily strapped.

There on, she swept aside the Czech 6-0 in the second set, before seeing through the third 6-4 to progress to the third round in Melbourne.

After the game, she confirmed that she had injured her psoas muscle, which is linked to the spine and the hip.

It was just a battle today. You've got to be able to play under all kinds of circumstances. I had to just calm myself down. In the middle of a match like that, you can get a little hysterical.

I guess if I got to the point where I just couldn't move at all, I guess I would have had to retire. I haven't retired from a match in a long, long time. I just go to the bitter end. It was bitter today, but it just didn't end.

Another title hopeful from US, eighth seed Andy Roddick, slammed 17 aces which helped him see off Russia's Igor Kunitsyn in a 7-6 (7), 6-2, 6-3 second-round victory.

The victory ensured Roddick progressed into the third round at Melbourne Park. After the victory, he said he felt comfortable on the court,

I think when you're confident, the court just makes sense; decisions come easier to you. A lot of it comes naturally. There's not a whole lot of thought process. You're not forcing a lot. The ball kind of, I guess, reacts the way you want it to. So I feel comfortable out there right now.