Two weeks after injuring his ankle stepping on a ball while playing tennis - it led to him pulling out of the PGA Grand Slam in Bermuda - Els returns for the WGC-HSBC Champions at Mission Hills.
"Amazing how things work - you hurt your ankle and then you come to the most hilly course in the world," the 43-year-old South African said. "It's basically on a mountain side.
"I'm on a bunch of painkillers and stuff. Whenever there are loose balls on a tennis court move them off please - I didn't do that and went down pretty hard.
"I basically did a Glenn McGrath."
Australian fast bowler McGrath trod on a ball in the warm-up for the second Ashes Test in 2005 and missed the match.
Winning the last world championship of the season could take Els from ninth to second on the European Tour's "Race to Dubai" standings - except his name is expected to be removed from the money list in the coming days.
This week is only his 10th Tour appearance of the season and he would have to play 13 tournaments to be included, but he is not entered for the Singapore, Hong Kong or South African Opens.
Order of Merit leader Rory McIlroy is controversially on a week off - he and Tiger Woods chose not to stay on in China after a duel on Monday reported to have earned each of them a seven-figure sum - and he could be overtaken at the top by Peter Hanson or Justin Rose.
Like Els, however, Rose is planning a fortnight's rest after this week whereas McIlroy is playing in Singapore and Hong Kong before the race-ending World Tour Championship in Dubai.
Rose's sixth place finish in Shanghai last week was his eighth top-10 finish in 11 European Tour starts this year, but with Hanson winning and McIlroy second he lost ground.
"This is a big week," the 32-year-old world number five said.
"I'm in Rory's hands to a certain extent and I have to win this week to give myself a chance."
McIlroy and Woods are not the only big names to have turned the event down. Webb Simpson and Matt Kuchar, respectively the US Open and Players Championship winners, are also missing and among the other Americans to stay away are Steve Stricker, Hunter Mahan, Jim Furyk and Rickie Fowler.
Ten of Europe's Ryder Cup side are present, Sergio Garcia having undergone an eye operation since the match in Chicago, but only six of the American team - Phil Mickelson, Bubba Watson, Keegan Bradley, Jason Dufner, Dustin Johnson and Brandt Snedeker.
Lee Westwood has won all round the globe, but so far that has not included a major or a world championship - and this is his 100th attempt.
"I do love coming to this part of the planet, but I would have preferred not to have brought a chest infection with me," Westwood wrote on his website.
"I think the kids started it all and then (wife) Laurae passed it on as a going away present.
"You wouldn't want to be a caddie this week because it's going to be a stamina test on this hilly lay-out.
"And where to next on my Jules Verne journey? Well before I emigrate to America at the end of the year I'll have taken in Dubai, South Africa and Thailand.
"Will need a new passport soon."