Gatlin, unbeaten in 16 races coming into the finals in Brussels, set a personal and season's best time in a strong 100 metres and followed that up an hour later by destroying his rivals in the 200 metres.
If he wins his final race in Italy's Rieti on Sunday, he would become the first male sprinter to go through an entire season unbeaten since Usain Bolt in 2009, taking full advantage of the Olympic and world champion's exceptionally lean season.
In the 100 metres, Gatlin flew out of the blocks and crossed the line in 9.77 seconds, metres ahead of a strong field, all of them sub-10 seconds men.
Fellow American Mike Rogers was second in 9.93 and Jamaica's Asafa Powell third in 9.95. Gatlin's defeat of Rogers also made him the official 2014 Diamond League champion for the distance.
Gatlin, whose last defeat was his fourth-place finish a year ago in Brussels, took to the track again an hour later, destroying an arguably weaker 200 metres field.
His 19.71 seconds was three-hundredths of a second outside the season and personal best he set in Monaco in July. Qatar's Femi Ogunode was a distant second, several metres back in 20.15.
The 32-year-old Gatlin, who won Olympic gold for the 100 metres in 2004 and was world champion at both 100 and 200 metres in 2005, served a four-year doping ban from 2006-2010, but said he was getting better with age.
He was second behind Bolt in last year's world championships and said he wanted to challenge the Jamaican next season.
"Why not? It's not just one lane on the track when it comes to the 100 metres or any other event," he told reporters. "I feel the world wants to see a good rivalry... That's what track and field is all about."
Bolt had won the 100 metres in Brussels for the last three years but was absent from Friday's season-concluding event after a poor season by his high standards.
He missed races early on with a foot injury, helped the Jamaican relay team win Commonwealth Games gold at the start of August and only dipped below 10 seconds in Warsaw two weeks ago.
HIGH JUMP SHOWDOWN
In the women's 200 metres, Olympic champion Allyson Felix proved she is the queen of the longer sprint, setting a season's best 22.02 seconds and also taking the title of Diamond League champion in her event.
"It's been a tough season with a lot of bumps along the way," she said. "I knew I would eventually get healthy again and hope to get another three quality years."
The evening's other highlight was a high jump showdown between Qatar's Mutaz Essa Barshim and Ukraine's Bohdan Bondarenko.
The Qatari won with a leap of 2.43 metres, the best in the world this year and beating his own Asian record by a centimetre, before each man tried, but failed, to surpass 2.46.
The 21-year-old record of 2.45 metres by Cuba's Javier Sotomayor still stands.
Earlier in the evening, New Zealand shot putter Valerie Adams, twice Olympic champion, improved on her own 2014 best with a 20.59-metre second round throw which also broke a 27-year-old meeting record.
Another double Olympic champion, Czech javelin thrower Barbara Spokatova, threw a season's best 67.99 metres.
In total seven season's best throws and runs were set on Friday.
(Reporting By Philip Blenkinsop; Editing by Rex Gowar)
Share
