British light-heavyweight Buatsi secured a victory yet unimpressive debut to life under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a majority decision in a competitive 10-round contest at the boxing arena.
But Parker landed significant shots, landing some telling clean blows in a fight where the styles failed to mesh, with frequent clinching disrupting the action.
The scoring judges scored it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my best showing but what do champions do? They prevail," the victor said in the arena as he was faced boos from the crowd.
The British fighter got back to winning after his initial pro loss - an thrilling contest with his previous opponent in February - to secure a twentieth professional win.
Some ringside observers believed the challenger, 31, should have been awarded the win but the contender suffered the second setback of his 28-match career.
The Champion Earns Victory in Uneventful Affair
The fighter's advancement has stalled in recent years through contract problems and considerable time of inactivity.
Once tipped as the future of UK boxing, he now finds himself trying to realize his potential - maybe in what appears to be a last chance - under new promotional backing.
He began cautiously, with the two boxers willing to be aggressive in a tentative initial rounds.
Parker, whose sole prior loss came at super-middleweight against his former opponent in two years ago after suffering a hand injury in the contest, was competing in only his second bout at light heavyweight.
By the halfway stage, the underdog had made it competitive, making life awkward for Buatsi, who utilized a tight guard to barely take the better stanzas.
The spectators' acceptance decreased during frequent holding, with the challenger going down several times during close exchanges.
Parker finished the stronger, but many rounds were hard to judge. However, previous titleholder Carl Frampton - providing analysis for Dazn - had it particularly wide for the challenger, awarding Buatsi just a single round.
The victor progresses, but with the caliber of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still appears challenging.
Hatton Homage Motivates All-Manchester Contest
In the co-main event, Lyndon Arthur defeated Rea by split-decision in a outstanding local rivalry contest to secure the European light-heavyweight championship.
The venue fell silent for a extremely emotional memorial ahead of the contest as 10 bells rang in memory of Manchester's own Ricky Hatton, who succumbed aged 46 in September.
It was the premier televised match card in the city since the passing of Hatton. As the final chime faded, the stillness transitioned to a shout of "there's only one Ricky Hatton".
The competition within the ring reflected the sentiment. Arthur was sent to the canvas by a significant blow directly to the face in the initial stage, rising shakily to his position on the eight count.
But the Manchester United-red shorts of the fighter soon pressed ahead again. From the other corner, Rea - in rival City blue - was damaged quickly, noticeable damage forming under his orbital area as the duo landed hard punches.
Rea, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the pace seldom decreased over 12 rounds.
The victor barely secured the decision with scoring tallies of 114-114, close margin and wider gap, but the two athletes were determined and courageous, exactly what their idol Hatton stood for.
