British light-heavyweight Buatsi secured a victory yet unimpressive beginning to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a competitive ten-round bout at the Manchester venue.
But Parker landed significant shots, landing some telling single shots in a match where the techniques didn't complement each other, with excessive holding disrupting the contest.
Two judges scored it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my greatest showing but how do champions respond? They win," Buatsi said in the ring as he was greeted with disapproval from the audience.
The British fighter bounced back after his initial pro loss - an epic battle with Callum Smith in February - to earn a 20th pro success.
Various analysts believed Parker, 31, should have been awarded the decision but the Derbyshire fighter experienced the second loss of his 28-match professional journey.
Buatsi Secures Victory in Uneventful Encounter
Buatsi's progress has slowed in recent times through promotional disputes and extended periods of lack of fights.
Once tipped as the rising talent of the British fight scene, he now finds himself trying to realize his potential - perhaps in what appears to be a final roll of the dice - under new promotional backing.
He started carefully, with both competitors willing to be aggressive in a cagey opening few rounds.
Parker, whose single earlier setback came at the lower weight class against his former opponent in 2022 after breaking his hand in the contest, was making just his second fight at light-heavyweight.
By the halfway stage, Parker had kept it close, making life awkward for Buatsi, who operated with a solid defense to narrowly win the more effective rounds.
The audience's tolerance wore thin because of regular grabbing, with the challenger slipping to the canvas multiple occasions during clinches.
Parker closed well, but many rounds were challenging to assess. Although, previous titleholder the boxing analyst - working with the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just one round.
Buatsi moves on, but with the presence of power puncher David Benavidez, and Russian champion Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Hatton Tribute Inspires All-Manchester Fight
In the co-main event, Lyndon Arthur defeated Bradley Rea by divided decision in a outstanding all-Manchester contest to secure the European light-heavyweight title.
The arena became quiet for a profoundly moving memorial before the fight as a bell ceremony rang in honor of Manchester's own Hatton, who succumbed at age 46 in September.
It was the initial significant broadcast match card in the city since the passing of Hatton. As the concluding sound faded, the silence gave way to a shout of "only one Ricky Hatton".
The fighting during the bout matched the sentiment. Arthur was knocked down by a powerful punch squarely on the chin in the second round, rising shakily to his footing on the count of eight.
But the traditional red shorts of Arthur soon pressed ahead again. On the opposite side, Rea - in rival City blue - was marked up soon, significant bruising forming under his eye as the duo exchanged powerful shots.
Rea, 27, connected with strong blows but the champion, 34, matched the intensity with effective uppercuts as the intensity rarely dropped over the full distance.
Arthur barely secured the verdict with scoring tallies of 114-114, 115-113 and wider gap, but both fighters were relentless and full of heart, all the qualities their hero Hatton represented.
