"When we talk about (competitive) pressure on the hand, we are talking about a period of around six months (before that is possible)," surgeon Radek Kebrle said in a televised news conference.

"She is a young athlete, healthy... but it still is a relatively massive injury," he said, adding that all the fingers on Kvitova's left hand were hurt as she grabbed the attacker's knife.

Her spokesman, Karel Tejkal, earlier described Tuesday's near four-hour operation as a success and said Kvitova's mood was optimistic.

But both he and the Women's Tennis Association suggested her future in the sport was uncertain.

"There will be several weeks of waiting with a splint and then, gradually, slowly she will be able to put the hand to work," Tejkal told Czech public television.

But any return to competitive tennis for the Czech world number 11 was "weeks and months" away, he said.

The WTA, the umbrella organisation for the women's professional game, said it regretted her absence from the circuit.

Unique power

"It's unclear if or when Kvitova will be back on the court, and the start of 2017 won't be the same without her unique power and competitive spirit," the association said on its website .

Aged 26, the hard-hitting left-hander rose to world number two in 2011 when she won the first of her two Wimbledon singles titles, and has been a mainstay of the top ten virtually ever since.

She slipped in the rankings this year but showed improved form in recent months, winning the Wuhan Open title in October and the season-ending WTA Elite trophy in November.

Czech police were still searching for her attacker, public television reported.

idr/(Reuters)