Williams, the 23-time grand slam champion, has not featured since lifting the Australian Open title in January, a feat she did while being two months pregnant.
The American has since given birth to daughter Alexis Olympia.
She will return to action in 2018 – although exactly when remains unclear – and Halep is looking forward to competing with her again despite Williams' dominance in recent years.
"I think we miss her. In my opinion, I miss her," she told Omnisport, speaking courtesy of Hublot.
"The tournaments were more open when she was not playing. But now that she is coming back, I think it's great for the sport.
"It shows that she's very ambitious and she has a big desire to play tennis again, which is great. I'll always admire her."