Phil Healy produced a season's best run in the 200m heats but admitted her mixed relay commitments had left her not as sharp as she could have been.
Healy, 26, was hoping to run a personal best and to qualify for the semi-finals but finished fifth in her heat, which included the new Olympic 100m champion, Elaine Thompson-Herah of Jamaica.
The Cork sprinter's time of 23.21 seconds left her three places short of qualifying, but she still has the 400m heats to come on Tuesday.
Healy said that she has felt the exertions of getting to an Olympic final with the mixed relay team.
“It's disappointing initially but I went out there and gave it my all, and it is a season's best," she remarked.
"I knew I was coming in in PB shape, but obviously there is going to be that fatigue factor with the two relay rounds before this.
"Obviously I would have loved to run quicker, but look, coming in I had to sacrifice my own individual (event) to a certain extent for the relay.
"But if you asked me a couple of weeks ago if I wanted to be an Olympic finalist, of course I would have taken that over anything.
"When you turn to the individual of course you want to progress, and it was a season best, after two all-out 400 metres in a matter of days beforehand, before coming out here at the crack of dawn in the morning.
“I’m the first Irish person to qualify in three events, so I am going to go out tomorrow and give it my all, anything can happen it’s a new day."
