Milos Raonic has been forced to withdraw from this week’s BNP Paribas Open in Indian Wells.
The world number four has yet to recover from a hamstring injury, one which forced him to miss the recent Delray Beach Open final in which he had been due to face Jack Sock.
Raonic’s withdrawal means former US Open champion Juan Martin Del Potro will be the 32nd seed when the draw is made at 2300 GMT on Tuesday.
Andy Murray heads the field at an event he has never won.
Novak Djokovic, Rafael Nadal and Australian Open champion Roger Federer are also in the line-up for the first Masters 1000 tournament of the ATP season, as are Murray's fellow Britons Dan Evans and Kyle Edmund.
Meanwhile, the women’s draw was made on Monday and it a threw up a possible second-round metting between Brits Johanna Konta and Heather Watson.
As 11th seed, Konta receives a first-round bye. Watson, who has just slipped out of the world’s top 100, will need to beat American Nicole Gibbs if she is to meet her compatriot.
Naomi Broady will not be making it three Britons in the main draw, though. She crashed out in the first qualifying round as Tereza Martincova fought back to win 4-6 6-2 6-3.
Serena Williams is the top seed but her world number one status is on the line in California with Angelique Kerber looking to wrest it back.
Williams is seeded to meet French Open champion Garbine Muguruza in the quarter-finals and Karolina Pliskova in the last four.
In the bottom half of the draw, Kerber will meet Agnieszka Radwanska in the last eight and Simona Halep in the semis if the seedings play out.
The women's main draw action begins on Wednesday with the men's event starting 24 hours later.
