"It's bad. It's not right," said Polish men's doubles player Michal Logosz after organisers announced that some 60 percent of the matches, mostly in the doubles draws, would be affected by the changes to the tournament which starts on Saturday.
"It's the most important competition. It's crazy that they can't do the draw how they are supposed to," said German doubles player Johannes Schoettler.
The Badminton World Federation (BWF) apologised to the players after it emerged that the original schedule published on Wednesday had not followed the competition regulations as agreed with the International Olympic Committee (IOC).
"There was an oversight and it's human error that this had not been carefully checked by our own team and myself at the outset," tournament referee Torsten Berg said.
"But of course if somebody had expected to have a late morning on Saturday and they now have to play early they will be disappointed," he added. "We understand that and we are sorry about this happening but see no choice other than to apply the BWF regulations and our agreement with the IOC."
The tournament at Wembley Arena begins with pools of players competing in round-robin matches.
Schoettler said he and partner Ingo Kindervater had already prepared for an early game against Australia and now faced Taiwan in an evening match instead.
"I started getting up early the last few days to get ready.
We should have played Australia, the weakest in our group," he said after a training session.
"My brother SMS-ed me this morning to say we now play Chinese Taipei, our most important match, and now on Saturday evening.
"It's stressful. We have moved to Wembley Plaza Hotel because we play tomorrow. "We could have stayed in the Olympic Village one more night and everything (would have) been easier."
Logosz said the scheduling changes had played havoc with the plans of family and friends.
"This is really bad," said Logosz, who will partner Adam Cwalina against South Korea's Ko Sung-hyun and Yoo Yeon-seong on Saturday.
"It's never happened before and it happens in the Olympics -- it's not right. For me it's not really bad but for mixed doubles, two matches in one day, this is a disaster. Maybe they will do something about that.
"We have tickets for families and friends and we found out only 24 hours before the matches."
- Michal Logosz