Story highlights US women's 4x100-meter team into final

The US was hit by Brazil during the 4x100-meter relay, causing a botched handoff

The US appealed the result and allowed to re-run race

(CNN) The anguish was clear on Allyson Felix's face -- but the relief will be even more palpable.

Team USA are into the women's 4x100m relay final Friday, but only after a bizarre day on the track in Rio.

It all started Thursday morning.

Felix, the second leg on Team USA's 4x100-meter relay team, was about to hand off the baton to her teammate, English Gardner.

But then, disaster struck. Just as she was about to pass the baton, Felix was hit by a Brazilian runner who veered into the US lane. It caused Felix to trip, bungling the exchange. The baton was dropped.

Read More