Christian Malcolm finished fifth in the 200m final, left in the wake of world record-breaking winner Usain Bolt.
The Jamaican blasted home in a stunning 19.3 secs, USA duo Shawn Crawford and Walter Dix taking silver and bronze.
Churandy Martina and Wallace Spearmon finished second and third but were later disqualified, moving Newport's Malcolm, 29, up into fifth spot.
"I didn't run the best bend and wasn't good enough, but Beijing has been great," said Malcolm who ran 20.4 secs.
"I have made the final and I am injury free, so I can move on and build from this.
"I am improving so I am looking forward to next season."
The Welsh sprinter, who ran a season's best of 20.25 secs to make the final, was as awed as the rest of the Bird's Nest Stadium by Bolt, who also claimed gold with a world record in the 100m on Saturday.
"You have got to keep going because he [Bolt] is going to have a bad day some time," Malcolm told BBC Sport.
"He has had a great championships and got it right on the day."
Malcolm won the sprint double at the 1998 Junior World Championships, the same year that he claimed silver at the Commonwealth Games.
He was fifth at the Sydney Olympics in 2000, but faced heartbreak before the 2004 Athens Games when he suffered a serious kidney complaint that required hospital treatment.
Malcolm could only finish seventh in the semi-final of the 200m then, and has since been hampered by groin and hamstring injuries since.
Men's 200 metres final:
1. Usain Bolt (Jam) 19.30 (WR)
2. Shawn Crawford (USA) 19.96
3. Walter Dix (USA) 19.98
4. Brian Dzingayi (Zim) 20.22
5. Christian Malcolm (GBR) 20.40
6. Kim Collins (SKN) 20.59
Churandy Martina (AHO) - DQ
Wallace Spearmon (USA) - DQ
~RS~q~RS~~RS~z~RS~30~RS~)