Des Moines - Allyson Felix struggled through her first race in 13 months but declared herself happy to be back after scraping into the 400m semi-finals on the opening day of the US Championships here on Thursday.
More than a year after her last outing as a professional, the 33-year-old Felix is back on the comeback trail at Drake University this week, hoping to win a berth on the US team for September's World Championships in Doha.
Felix, the only woman to win six Olympic track and field gold medals, is returning to the sport following her pregnancy and birth of her daughter in November.
However the comeback didn't go as smoothly as planned on Thursday, finishing fourth in her heat in a time of 52.20, well outside her personal best of 49.26 set in 2015.
That left the veteran former 200m and 400m world champion sweating on the outcome of other races to confirm her spot in the next round.
"It felt rusty, kind of to be expected," Felix said afterwards.
"I haven't raced in a long time. It's going to take some time to get back into it."
Felix, who is aiming to race in her fifth Olympic Games in Tokyo next year, was able to draw positives from the display however.
"Even though it wasn't a great result for me, it's a starting point," Felix said.
"My biggest goal is next year."
Felix said regaining her physical conditioning while juggling parenting duties had been the most demanding part of her comeback.
"Things that were pretty easy for me are now pretty challenging," Felix said.
"So just getting past that, and being a mom.
"I'm a regular mom, at the hotel I'm cleaning bottles and changing diapers, and getting ready for racing."
Elsewhere Thursday, there were few surprises as the four-day meeting got under way.
In the 100m, world champion Justin Gatlin and rival Christian Coleman breezed through their early heat.
The 37-year-old Gatlin, gold medallist in the 100m at the 2017 World Championships in London, clocked 10.16 to qualify second fastest behind training partner Isiah Young in 10.14.
Coleman, the world's fastest man over 100m this season with a world leading 9.79, barely needed to get out of first gear to win his heat in 10.29.
Coleman is in the vanguard of a new generation of US sprinters looking to replace Gatlin and the retired Usain Bolt at the pinnacle of international sprinting.
But the prospect of Gatlin and Coleman going head-to-head at this week's four-day meeting - the US qualifier for the World Championships - is uncertain.
Gatlin, as the reigning world champion, is not required to qualify for the world championships, and hinted on Thursday he may skip the later rounds of the 100m.
"I'll go back tonight and watch the race and see if there's certain things I can work on, and if there is something I can definitely work on and I think it's a positive step, then I'll be back tomorrow," Gatlin said.
Coleman meanwhile was less than fully satisfied with his opening display despite an easy win.
"It felt okay, pretty sloppy," the 2017 100m silver medallist said.
"There's definitely some things I can clean up."
In other early heats on Thursday, rising 400m hurdles star Rai Benjamin safely navigated his opening race to post the fastest qualifying time of 49.61.
The time was more than two seconds slower than Benjamin's fastest time of 47.16.
However Benjamin, the son of former West Indies cricket international Winston Benjamin, coasted home over the last 50 metres, suggesting he has plenty left in the tank.
"I wasn't gunning it, I could have run it a lot faster," Benjamin admitted later.
In the men's 400m, favourite Michael Norman comfortably qualified for the second round after winning his heat in 44.81.
Elsewhere, Molly Huddle romped to a fifth straight national title in the women's 10 000m, booking her place in Doha in a time of 31:58.47.
The men's 10 000m final was won by Lopez Lomong, a refugee from South Sudan who represented the United States at the 2008 Olympics. Lomong took the tape in 27:30.06.