Kim Clijsters was knocked out of the UNICEF Open in Gen Bosch on Tuesday.

The top-seeded Belgian lost 7-6 (5), 6-3 to Romina Oprandi from Italy in the second round of the Dutch WTA grass court tennis tournament. She also suffered a right ankle injury and is doubtful for Wimbledon, which starts next week.

"I will undergo some tests maybe tonight or tomorrow morning," said Clijsters at the post-match press conference. "Then I can give more specific answers. At the moment I just focus on getting my ankle better. Too bad it happened. It puts me back to where I was a few weeks ago. It's frustrating of course, but it's what an athlete has to deal with."

Clijsters suffered the injury in the second game, but was able to continue. Before Roland Garros, where she lost to Arantxa Rus in the second round, she had just recovered from the same ankle injury.

The world No. 2 had troubles in the first set, but managed to make it to a tiebreak. However, she lost the tiebreak 7-5. In the second set Romina Oprandi took the initiative immediately and finished the game winning 6-3.

"My game was not good enough," said Clijsters. "I tried, but it did not work out. I was hitting the ball well in practice. So I was not worried too much. I was only trying to bring across what I was really doing well in practice to my matches. I felt that I had a good mentality on the court to achieve that."

In the quarterfinals, Oprandi will meet Japanese veteran Kimiko Date-Krumm, who beat Lourdes Dominguez Lino from Spain 7-6 (3), 6- 0.