British light heavyweight Buatsi made a winning yet disappointing debut to his career under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a judges' verdict in a competitive ten-round fight at the Manchester venue.
But Parker had his moments, delivering effective individual punches in a contest where the approaches didn't complement each other, with frequent clinching disrupting the action.
The scoring judges had it 96-94 to the winner, with the third a even score.
"It wasn't my finest display but what defines champions? They prevail," Buatsi commented in the ringside as he was met by boos from the spectators.
The Londoner bounced back after his initial pro loss - an thrilling contest with Callum Smith in February - to secure a 20th career victory.
Various analysts believed Parker, thirty-one, merited the win but the contender suffered the second defeat of his 28-fight career.
Buatsi Earns Win in Slow Match
Buatsi's progress has stalled in recent times through promotional disputes and long spells of lack of fights.
Once tipped as the next star of British boxing, he now finds himself trying to achieve expectations - possibly in what appears to be a final roll of the dice - under recent support.
He started carefully, with both competitors prepared to overcommit in a tentative opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in 2022 after suffering a hand injury mid-fight, was participating in his second appearance at the higher weight class.
By the fight's midpoint, the underdog had stayed in contention, making life awkward for the favorite, who utilized a solid defense to edge the more effective rounds.
The spectators' acceptance wore thin amid constant clinching, with Parker slipping to the canvas several times during clinches.
Parker closed well, but many rounds were difficult to score. Nevertheless, ex-champion Carl Frampton - working with the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just a single round.
The victor moves on, but with the likes of hard hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still seems difficult.
Ricky Hatton Memorial Fuels Manchester Derby Battle
In the supporting bout, Arthur beat Rea by split-decision in a terrific all-Manchester battle to secure the European light-heavyweight belt.
The arena became quiet for a profoundly moving memorial ahead of the contest as a bell ceremony rang in remembrance of the city's native Hatton, who passed away 46 years old in last month.
It was the premier televised boxing event in the city since Hatton's death. As the concluding sound ended, the stillness transitioned to a shout of "there's only one Ricky Hatton".
The competition within the ring equaled the emotion. Arthur was knocked down by a left hook directly to the face in the second round, standing uncertainly to his footing on the eight count.
But the traditional red attire of the fighter soon advanced again. On the opposite side, Rea - in competitive blue - was damaged soon, noticeable damage forming under his eye as the fighters landed hard punches.
The challenger, 27, landed power punches but the champion, thirty-four, matched the intensity with effective uppercuts as the pace seldom decreased over the full distance.
Arthur barely secured the result with official scores of 114-114, close margin and 115-112, but the two athletes were persistent and brave, all the qualities their inspiration the legend stood for.
