SERENA WILLIAMS said today that preparing for her return to tennis following the birth of her first child has been difficult and she still has doubts about how she can “keep going.”

Williams makes her comeback to the WTA Tour this week when she takes on Kazakhstan’s Zarina Diyas in the opening round of the Indian Wells Masters.

The 36-year-old was last in action 14 months ago when she clinched her 23rd grand slam singles title by winning the Australian Open.