– Gymnastics never has been a sport for the faint of heart. At the Olympic trials, all that flying, flipping and twisting becomes even more nerve-wracking, with the uncompromising eye of Martha Karolyi judging every move and Olympic berths on the line.

As if that wasn’t difficult enough, Maggie Nichols carried an added burden into Friday’s opening night of the trials at SAP Center. The Little Canada gymnast, still working her way back from a knee injury, was performing all four events for the first time since early March. Though she wasn’t perfect, Nichols was proud of an evening that left her in eighth place in the all-around standings.

Not even her best friend, the incomparable Simone Biles, was flawless on the first of two nights of high-pressure competition. Biles, the reigning U.S. and world all-around champ, leads the field of 14 with a score of 61.850 despite a major wobble during her balance beam routine. The fast-rising Laurie Hernandez is second with 60.850, and 2012 Olympian Aly Raisman is third with 59.950.

Nichols started and finished well, scoring 15.100 for her double twisting Yurchenko vault and 14.900 for the first full floor exercise routine she has done in three months without a spotter on the mat. But she fell off the beam while executing a side aerial, scoring a 13.700.

Two weeks ago at the U.S. championships, Nichols’ knee prevented her from even competing on vault and floor. Friday, she fought through her mistake and finished with an overall first-day score of 58.250. The five-member Olympic team will be announced Sunday after the second day of competition.

“I’m really proud of myself,” Nichols said. “I hit the best I could. I’m a little disappointed with beam. Everything was so solid, except for that side aerial.

“The pressure wasn’t too bad. I was really confident and really excited to compete. And I also just wanted to come out and enjoy it and take it all in, which I did.”

The all-around champion at the trials will automatically qualify for the Olympic team. A committee headed by Karolyi will pick the other four athletes and as many as three replacements, based on performances at the trials and at last month’s U.S. championships.

At this point, Karolyi said, she knows the routines and capabilities of everyone in the group. Her mission at the trials is to see who can thrive — and who would wither — under a spotlight as hot as a summer at her Texas ranch. That is what the Americans will face in Rio, and Karolyi wants the trials to replicate that pressure.

Biles wasn’t thrilled with her performance, looking visibly unhappy after her beam routine. She was executing a turn when she nearly fell, but she hung on. Because she was so focused on the dismount, she said, she took the turn for granted.

“I don’t know the last time that happened,” said Biles, who had the night’s top scores on vault (16.000) and floor (15.700) and still was second on beam (15.200). “I was just happy to go out there and perform under the pressure. It felt like your heart was going to pop out of your chest. It was kind of hard to control your adrenaline.”

Nichols tore her meniscus in early April, had arthroscopic surgery and did not return to competition until the national championships, where she performed only on beam and bars. Her coaches with the Twin City Twisters, Sarah Jantzi and Mike Hunger, said she had gained strength and confidence in the two weeks since that competition.

The three have been rushing to get Nichols up to speed after her long recovery period. Hunger said her mistake on beam was “a fluke,” and he expects her to be better on the second day of competition Sunday. Nichols explained that she was crooked when she began the move and was “super disappointed’’ that she had no way to stop herself from falling.

“She’s in good spirits, and she’s very relaxed,” Hunger said. “She wasn’t rattled. She’s close to 100 percent physically on the knee, but it’s the lost training time we’re fighting against.”

Karolyi said Nichols did “a decent job,’’ but she has more to prove Sunday. “Maggie looks like she would need a little bit more time to get back the sharpness that she had last year before the world championships,” she said.

Nichols was one of several gymnasts bedeviled by the beam.

Gabby Douglas, the reigning Olympic all-around gold medalist, also fell and is tied Nichols for 10th place in the event. Douglas, who was fourth at the U.S. championships, is in seventh place in the all-around standings.

Nichols said she still felt confident and strong Friday night, and Hunger believes she still has a chance to make the team.

“Do not count her out yet,” Hunger said. “The kid’s a fighter. And she’s got nothing to lose now.”