Lord Coe admitted he was far from "eulogistic" to see twice-banned American sprinter Justin Gatlin win the 100 metres at the World Championships in London.
Coe, president of the International Association of Athletics Federations (IAAF), conceded it was "not the perfect script" for Gatlin to triumph on what many hoped would be Usain Bolt's night.
In Bolt's final individual race before retirement, the 11-time world champion could only take third place, behind United States sprinters Gatlin and Christian Coleman.
"Sport rarely settles upon the perfect script. Life's just not like that," Coe said.
Speaking on BBC 5 Live's Sportsweek, Coe added: "It's not the worst result ever.
"I'm hardly going to sit here and tell you I'm eulogistic that somebody that has served two bans in our sport would walk off with one of our glittering prizes, but he is eligible to be here."
Coe said that as head of the IAAF he would have to congratulate Gatlin if their paths crossed in London.
"I will say, 'You were eligible to compete here and frankly' - as Usain Bolt said to him last night - 'you have worked hard for what you have achieved'," Coe said.
"I think the journey to that point is not a comfortable one for me."
He added: "It's not the perfect script."
Gatlin, who returned from his second suspension in 2010 after four years out of the sport, has found himself cast as the pantomime villain in his battle with Bolt.
He was roundly booed once the crowd in London's 2012 Olympic stadium realised Gatlin had crossed the line first on Saturday night.
Coe stressed the IAAF tried to effectively end Gatlin's career following his second failed drugs test in 2006, only for court action to see his suspension reduced.
"There have been two bans in the past, one which got watered down which made it very difficult for the second ban," Coe said.
"The second ban we went for an eight-year ban which would have in essence been a life ban - we lost that.
"So these things are suffused in legality."
Coe said he was "never going to close the door" on the prospect of life bans for drug offenders, saying "the majority" in athletics would favour them being available as a punishment.
"We have tried it, we've constantly tried it," he said.
"We've lost it in a mixture of courts and particularly the Court of Arbitration (for Sport)."
Gatlin was set to return to the stadium on Sunday to receive his gold medal, and it seemed inevitable he would face more heckling from spectators.
"It's not the most exciting day in prospect for me - but he is eligible to compete," Coe said, when asked about the medal ceremony.
"He has to be accorded some respect."
Coe added: "I don't think Usain will want a situation where an athlete at that point is demonised. But people will respond the way they need to."
Two-time former Olympic 1,500 metres champion Coe has found encouragement in the public reaction to doping in athletics.
"What I take comfort from is that people do care about this," Coe said. "And while they're caring that means we've got hope here."
Gatlin won in 9.92 seconds at the London Stadium, with Coleman taking silver in 9.94secs and Bolt the bronze in 9.95s.
Beaten into silver at the previous two World Championships and last summer's Olympics, the 35-year-old Gatlin finally found a way to win, but was more intent on heaping praise on his departing rival than basking in his own glory.
"Bolt is an electrifying character who has run sizzling times, mind-blowing times and throughout the years he has always kept it classy," Gatlin said.
"He's inspired me to be a stronger, faster competitor and I've only wished every year to be his top rival.
"Win or lose, he's the man and the first thing I did when I crossed the line and saw that I won, I paid homage to him, because he deserves it. Usain is a Goliath."
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