This announcement was made by the Badminton Association of Malaysia's president Tan Sri Tengku Mahaleel Tengku Ariff on Monday.
He said Chong Wei has proven that he was still Malaysia's number one player by defeating South Korea's Lee Dong Keun 21-12, 21-10 in the Sudirman Cup competition last night and would be replacing Chong Wei Feng.
Yesterday's match was the first competitive outing for Chong Wei after being out of action for eight months due to a doping ban.
"Chong Wei has played very well and we have decided to include him because of his performance last night. Not to send him would deprive our nation of a chance to win a medal.
"Between Wei Feng and Zulfadli, Wei Feng is much older and has been to the World Championships twice.
"Zulfadli, he is still young at 23, we decided that given the principle, philosophy that we have, we decided that Zulfadli will go for the championships," Ariff told reporters.
The Badminton World Federation (BWF) only allow two singles players from each country to compete in the tournament and with Cong Wei only ranked at 45 the better ranked Wei Feng, ranked 31st and Zulfadli 41st were initially chosen.
Ariff confirmed that BAM would continue to support Wei Feng to qualify for the 2016 Olympic Games in Rio de Janeiro, Brazil.
"We have spoken to Wei Feng and he is very positive with the decision. He realises BAM's programme now and we reassured him that we will give him full support to qualify for the Rio Olympics," he added.