"It will also boil down to that particular day, who is in the right mental and physical conditions on that day to pull through. So it is still very open, anybody from these six girls can be 1-2-3," he said.
Vimal said there is still a lot of time and Sindhu needs to work on her strategies against potential opponents.
"A lot can be done like they can discuss about her potential rivals, can look and analyse the matches: what situation they lost a match, the errors that they committed. It helps devise tactics and also gives confidence to the players. They still have time as Olympics is still a month away," he advised.
The 58-year-old, who had represented India at the 1992 Games, believes B Sai Praneeth has a good tactical game and may emerge as a dark horse in the men's singles at the Olympics, beginning July 23.
World number 15 Praneeth had ended a 36-year-long wait by winning the bronze medal at the World Championship in 2019.
"As a junior, I always felt he will achieve more than anybody else. He is the first one to do well in World Championship after Prakash (Padukone), so there is no reason why he can't do well in Olympics.
"If he gets a good draw, he can be a dark horse,” said Vimal, who was the chief India coach from 2001 to 2006.
"I don't know what physical state he is in but you never know. If you don't run into a big player early on in the draw, chances of going far is more in Olympics than a Super Series event.
"It again depends on mental and physical strength to last out, game wise, tactics wise, he is all good."