Gold medal favourite Shelly-Ann Fraser-Pryce was the only athlete to post a sub-11 second time during the heats of the women's 100m at the Olympic Games on Friday.
The diminutive Jamaican's time of 10.96s in heat four was enough to finish 0.05s ahead of Marie Josee Ta Lou of Ivory Coast in the fastest of the eight heats.
The two-time defending Olympic champion from Jamaica hasn't been quite her best so far this season, and while she is undoubtedly the athlete to beat, several other athletes could potentially upset the triple world champion this time around.
In the first heat, Great Britain’s Desiree Henry posted a time of 11.08s and in the process upset former World Championship runner-up Murielle Ahoure.
The silver medalist at the 2015 Worlds Dafne Schippers recovered from a sluggish start to win heat four in a time of 11.16s, some 0.15 clear of Germany’s Tatjana Pinto.
The women's 100m is an event the US haven't won for 20 years, but American athletes did produce three heat winners on Friday/
The 2015 world bronze medalist Tori Bowie won heat three in 11.13, beating Nigeria’s Blessing Okagbare by 0.03.
In heat five, long jump specialist Tianna Bartoletta beat world junior silver medalist Ewa Swoboda by 0.01s to take the heat win in 11.23, while American champion English Gardner posted 11.09 to finish first in her heat, well ahead of South Africa’s Carina Horn in second.
World number one Elaine Thompson overcame a slow start to win heat seven in 11.21, just 0.04s ahead of local favourite Rosangela Santos.
Trinidad and Tobago's Michelle-Lee Ahye also impressed in the heats, winning heat six in a time of 11s flat, well ahead of compatriot Christania Williams.
Meanwhile, Malaysia’s Zaidatul Husniah Zulkifli failed to advance to the semi-finals after finishing in eighth place in heat eight with a time of 12.62.