ustin Gatlin's 100m triumph at the World Championships in London was "not the ideal content", says Lord Coe.
American Gatlin, 35, who has twice served a doping boycott, pulled off a stun win to end Usain Bolt's reign in the Jamaican's last individual race.
"I'm not eulogistic that somebody who has served two bans has strolled off with one of our sparkling prizes," said Coe, who is leader of games' administering body the IAAF.
"In any case, he is qualified to be here."
Jolt, 30, had been most loved to secure his twentieth worldwide gold in the last real titles of his sparkling vocation, yet the three-time 100m Olympic champion needed to make due with bronze, completing behind Gatlin and his USA colleague Christian Coleman.
Gatlin was booed by the group at London Stadium as he celebrated, however was grasped by Bolt on the end goal.
Why was Gatlin prohibited?
In 2001, when he was still at school, Gatlin was given a two-year suspension for taking a prohibited amphetamine.
He effectively contended this was because of pharmaceutical he took for a lack of ability to concentrate consistently scatter and was permitted to come back to rivalry following a year.
At that point, in 2006 - having won the 100m and 200m twofold at the 2005 World Championships in Helsinki - he tried positive once more, this time for testosterone.
Gatlin was prohibited for a long time, staying away from a lifetime boycott in return for his co-operation with doping experts. This suspension was split to four years on bid.
After Saturday's race, Jamaica's head administrator Andrew Holness conceded he might want to see competitors who come up short medication tests get life bans, saying: "It's the main way you're going to completely guarantee that individuals don't cheat in the game."
Accordingly, Coe included: "So would I thus would the lion's share of our game. I'm not going to close the entryway on lifetime bans yet we've continually attempted it and lost it.
"It merits recollecting that Gatlin's first boycott was for amphetamines, and the body of evidence against him was at the more genuine end. That at that point got diluted. We at that point had the second real encroachment. We connected for an eight-year boycott and again that got lost."
