SERENA WILLIAMS HAS reignited speculation that she could make a return to tennis, refusing to rule it out when asked and instead replying: “I don’t know. But she re-entered the tennis anti-doping testing pool in December, setting off the rumour mill, only to deny that she was making a comeback. I don’t know, I’m just going to see what happens.”Asked why she had re-entered the drug-testing program, Williams said: “Did I re-enter? “Whether that’s the mixed doubles at the US Open, whether that’s doubles with her sister somewhere, whether it’s singles, only she knows. “But there’s no other way to interpret that.”The Williams sisters won 14 Grand Slam doubles titles as a pair and three Olympic gold medals.