Simone Biles pulled out of two more events at the Olympics on Saturday, raising major doubts over whether she will compete again in Tokyo as Nigerian sprinter Blessing Okagbare was thrown out after failing a doping test.
US swimmer Caeleb Dressel powered to a third gold medal of the Games but his bid for a potential six titles was thwarted.
USA Gymnastics said the 24-year-old would sit out two more events.
“She will continue to be evaluated daily to determine whether to compete in the finals for floor exercise and balance beam.”
Elsewhere on Saturday Dressel established himself as the dominant male swimmer of the Tokyo Games as he smashed his own world record to win the 100m butterfly title for his third gold medal.
Dressel could win another two gold medals, having already won the 100m freestyle crown and the 4x100m relay title with his team.
His US teammate Katie Ledecky stormed to her third straight Olympic 800m freestyle title with a dominant swim to bank her fourth medal in Tokyo.
The morning action at the Olympic Stadium was overshadowed by Okagbare’s failed doping test.
The 32-year-old won the long jump silver medal at the 2008 Beijing Olympics.
On day two of the athletics programme, McLaughlin glided through her heat in 54.65sec while Muhammad won hers in 53.97 on a track that is producing fast times.
Pole vault world record holder Armand Duplantis of Sweden eased through qualification for a final missing his American arch-rival Sam Kendricks, who tested positive for coronavirus.
He finished in the silver medal position behind his elder sibling in the individual event at the 2016 Rio Olympics and took bronze behind him at London 2012.
Belinda Bencic of Switzerland takes on Marketa Vondrousova of the Czech Republic for the women’s singles title later in a tennis competition that lost big names Naomi Osaka and Ash Barty in the earlier rounds.
Zverev will face Russian Karen Khachanov in Sunday’s final.
And Li Junhui and Liu Yuchen can give China a second badminton gold in the men’s doubles final.