Two-time Masters Cup winner Lleyton Hewitt could miss this year's event in Shanghai in November as that is when his first child is due to be born.
Hewitt has already pulled out of the Paris Masters
The tournament runs from 13-20 November and Hewitt has made it clear which he regards as being more important.
"He will make a decision closer to the time, but if there was a chance he would miss the birth, he wouldn't play," said his manager Rob Aivatoglou.
"People will understand if he does, he's committed to being at the birth."
Roger Federer, Rafael Nadal and Andy Roddick have also all qualified for the eight-man event but Marat Safin has had to pull out.
Hewitt has recently had toe surgery and a groin strain, and pulled out of the Paris Masters on Friday, so his fitness is also a doubt.
"A couple of hurdles need to be overcome if he's going to Shanghai," said Aivatoglou.
"The baby and the timing of the birth is the main factor, but there are injuries as well."