Clark has not played since a T-30 finish at the Sony Open in January, and he cited the same injury when he withdrew from the Masters earlier this month. Despite more than three months without a competitive shot, the South African is currently No. 57 in the world and had qualified for the 64-man event at TPC Harding Park.
Clark is the second player to bow out from the limited field, as Luke Donald announced earlier this year that he will skip it to attend his brother's wedding. Donald will be replaced by world No. 65 Miguel Angel Jimenez.
At No. 66, Francesco Molinari is next in line to take Clark's spot, but the Italian tweeted last week that a wrist injury would keep him sidelined until at least the Spanish Open, held May 14-17. Should Molinari not be able to participate, the final spot would then go to No. 67 Mikko Ilonen.
This year's event will feature a new format, with each of the top 16 players seeded into separate, four-man groups. All participants will play three round-robin matches within their group before the 16 group winners advance to single-elimination match play.