Serbian tennis player Novak Djokovic and his girlfriend Jelena Ristic pose for photographers as they arrive at a fundraising dinner for the Novak Djokovic Foundation in London July 8, 2013. [Photo/Agencies]

Novak Djokovic is going to need to get into the swing of being a father.

The six-time major champion wrote on Thursday on Twitter that he and his longtime girlfriend, Jelena Ristic, are expecting a baby.

The posting said in part: "Jelena is pregnant!!! We will be parents soon! (hash)blessed."

In February, the 26-year-old Djokovic said he and Ristic would be getting married. They have been a couple for more than eight years. She runs his humanitarian aid organization.

The second-ranked Djokovic is taking a little time off with a right wrist injury but expects to return to action next month at the Madrid Masters.

In December, 17-time major champion Roger Federer announced he and his wife, Mirka, are expecting a child in 2014. They already are the parents of twin girls.