After Serena Williams' three-set loss to Ana Ivanovic in the fourth round of the Australian Open, Williams’ coach Patrick Mouratoglou credits the Serbian with applying massive pressure, but said Serena’s movement was compromised by a back injury.

Mouratoglou added that Serena sustained the injury in practice prior to her third-round win over Daniela Hantuchova and nearly pulled out of that contest 30 minutes prior, but decided to give it a go in in what the Frenchman called a “miracle.”

“I don't know how she won against Hantuchova because it was 10 times worse than today,” Mouratoglou told a small group of reporters. “Today was a combination of not being able to move like she usually moves and she was in bad positions, but also the fact that Ana played a great match. When you are not able to do what you usually do, and [Ivanovic] is succeeding every time she hits a shot, the pressure is bigger on you cause you don't see any solutions. The pressure got stronger and stronger.”

Williams, who owns 17 Grand Slam titles, came into the contest with a 25-match winning streak. She is a five-time Aussie Open champion, but in her last three visits to Melbourne has suffered two ankle injuries and now a back injury, all which contributed to her losses.

“The back was a problem for her to move correctly,” Mouratoglou said. “She was never coming forward to hit the shot, she was always waiting for the ball, she was always on the back foot and she was in a bad position, so when you are in a bad position you miss everywhere. She was soft today and Ana was particularly aggressive and she came in every time and did it very well.”

Mouratoglou doesn’t believe the injury is serious and believes that had Williams beaten Ivanovic, she would have been fine if a few days.

Williams has been asked to play the United States’ Fed Cup tie in Cleveland against defending champion Italy on February 8-9 and is unsure whether she will compete, but said that “We'll try.”