Bernard Lagat, the fastest man in the world this year, survived a scare before advancing to the semi-finals of the Olympic 1,500 metres on Friday.
The Kenyan, with a season's best of three minutes 27.40 seconds, was clipped by American Alan Webb 300 metres from the end of the second heat, partially dislodging his left shoe.
He struggled on with the shoe half off before managing to kick it free 100 metres from the end and then accelerated to finish second behind Spain's Reyes Estevez.
Moroccan Hicham El Guerrouj, seeking the elusive Olympic gold he needs to cap a wonderful career, looked to have recovered from the respiratory problems that have dogged his season when he cruised through to win the first heat in 3:37.86.
El Guerrouj, who fell in Atlanta and took silver in Sydney, waited at the end to shake hands with last-placed Roberto Caraciolo Mandje of Equatorial Guinea, who finished in 4:03.27, almost half a minute behind the world record holder but a national record.
Michael East, seeking to rekindle the great days of British middle-distance running, won the third and final heat in the fastest time of the night, 3:37.37.
The semi-finals are on Sunday with the final next Tuesday.