Gabby Douglas fell off the beam on the first day of the U.S. trials, leaving her in seventh place overall. (Kyle Terada/USA Today Sports)

After a shaky start to the U.S. Olympic trials Friday at SAP Center, Gabby Douglas needed a strong showing on her final event — the balance beam — to leave no doubt about her readiness for Rio.

The reigning Olympic all-around champion didn’t get it, with her routine marred by a wobbly balance-check at the start before she fell off the four-inch-wide beam altogether during a turn.

The poor mark on the apparatus (10th best among the field of 14) dropped Douglas from fourth in the standings to seventh when the final scores were tallied after the opening night of the Olympic trials.

After taking Saturday off to polish their skills, the gymnasts will return to the arena Sunday to compete their routines again, with the scores from each night counting equally. The five-woman Olympic team will be announced Sunday night, following the final phase of the competition.

Douglas, 20, the Virginia Beach native who exploded on the international gymnastics scene with her all-around gold at the 2012 London Games, vowed to finish strong Sunday.

“I am definitely going to recover because that’s what I do,” Douglas said after Friday’s performance. “I’m a fighter. And I’m definitely going to go in tomorrow and do really strong training. One thing I’m doing is just not give up.”

Only the event’s all-around champion will lock in her spot in Rio based on her showing at the Olympic trials. The other four will be chosen largely on their performance here, yet with subjective factors weighed, giving the selection committee the latitude to field the strongest group to contend for the coveted team gold.

The U.S. women have twice won Olympic team gold — in 1996 and 2012. Given the depth of talent in the sport, the Americans are heavy favorites to defend their title in Rio.

They will be led by Simone Biles, the 19-year-old from Spring, Tex., whose blend of artistry and power has set a new standard in the sport.

Biles overcame a rare, imperfect performance on the beam to preserve a solid lead heading into Sunday. Her 61.850 points lead second-place Lauren Hernandez, a 16-year-old who is in her first year competing at the senior level, by a full point (60.850). In third is 22-year-old Aly Raisman (59.950), whose three medals made her the most decorated U.S. gymnast in the 2012 Olympics.

Douglas is in seventh (58.550), with her 10th-place showing dragging down her third-place finish on uneven bars, fifth-place showing on vault and sixth-place finish on the floor exercise.

“Obviously like always, I could do a little better,” Douglas said. “I’m just going to take this and not get down and fight for every little thing and not give up.”

Despite her rough night, it would be difficult to imagine Douglas being omitted from the 2016 Olympic team, given her status as the reigning Olympic all-around champion and her versatility on all four apparatus.

While Martha Karolyi, the all-powerful national team director of U.S. women’s gymnastics, was clearly not impressed with Douglas’s work, she was quick to note that there is time for her to polish her skills in the four weeks that remain before the Olympics get underway.

Karolyi attributed part of Douglas’s shakiness to training that had been less than ideal in the month leading up to trials and included a last-minute change in the coach who works with her on the competition floor.

“In my opinion, you compete better if you train better. It just makes sense because your confidence level rises once you hit every routine in a training, so you don’t have to be nervous,” Karolyi said. “I’m pretty confident that all of these things will go on a good direction, and we can work it out. Certainly she has to perform [Sunday].”