Lee McConnell believes Laura Muir can run even quicker and lower the British 1500m record she set at the Anniversary Games in London on Friday.
Muir's time of three minutes 57.49 seconds was the second-fastest in the world this year, and broke Dame Kelly Holmes' 12-year-old record.
"She's not scared to go out and take on the best in the world," McConnell said.
"There's time for her to grow and improve on various aspects to potentially lower that time."
Muir, 23, said after the race: "I'm over the moon with that. It's not just any record: it's Kelly Holmes' Olympic gold medal record. It's great to have."
Former 400m runner McConnell, who won nine medals at major championships, was impressed with the way Muir dominated the field.
"It was an absolutely incredible run," McConnell told BBC Scotland.
"Laura is just such a gutsy runner and it's what I really love about watching her. She went out with the pacemaker, she wasn't afraid to do that, and then when the pacemaker dropped off Laura was able to take on the race herself.
"To break Kelly Holmes' record was incredible, really fantastic to see. She (Holmes) is an incredible athlete, so for Laura to go faster really is amazing."
"She's never been scared. I've never seen her in a race where she's just sat back and relied on a sprint finish which so many of them do.
"Laura likes to go out there and make them run hard, she likes to break them and that's how she comes out with the performances and the wins that she's been able to do over the last couple of years."
'Laura has the ability to win a medal in Rio'
Although impressed with Muir's form ahead of next month's Rio Games, McConnell warned that Brazil will be a different challenge entirely.
"Friday was a one-off race; Rio is going to be three runs and it becomes very tactical," said McConnell, who competed at three Olympic Games between 2004 and 2012.
"It just changes the dynamic and can make it very difficult for athletes. It also makes the 1500m a very interesting race for spectators because you really don't know what's going to happen.
"Laura will be thinking about getting through the heats, and once she's through the heats she'll be thinking about getting through the semi-final and into the final. Once she's in the final, like all the other girls in that race, she'll be trying to win a medal.
"Laura has certainly got the talent and ability to win a medal, but so do all the other girls that are going to be in that final. It becomes so tactical, and there's a lot more to lose."