UK light-heavyweight Buatsi earned a win yet unimpressive start to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a majority decision in a competitive ten-round contest at the boxing arena.
But Parker found success, connecting with powerful single shots in a match where the approaches never quite clicked, with excessive holding spoiling the contest.
The officials scored it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my best showing but how do champions respond? They succeed," the victor stated in the arena as he was faced negative reactions from the crowd.
The Londoner got back to winning after his maiden career setback - an thrilling contest with Callum Smith in last winter - to claim a 20th career victory.
Various analysts believed Parker, thirty-one, should have been awarded the victory but the contender suffered the second loss of his 28-match professional journey.
The Champion Claims Triumph in Dull Affair
Buatsi's progress has slowed in recent times through promotional disputes and extended periods of inactivity.
Once tipped as the rising talent of the British fight scene, he now finds himself trying to achieve expectations - maybe in what feels like a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter willing to overcommit in a cagey initial rounds.
Parker, whose single earlier setback came at super-middleweight against John Ryder in 2022 after breaking his hand mid-fight, was participating in his second appearance at the higher weight class.
By the middle rounds, the underdog had stayed in contention, creating difficulties for Buatsi, who utilized a tight guard to barely take the more effective periods.
The spectators' acceptance wore thin because of constant clinching, with the challenger falling to the floor various instances during grappling.
The underdog finished the stronger, but many rounds were difficult to score. Although, previous titleholder the boxing analyst - commentating on Dazn - had it particularly wide for the challenger, giving Buatsi just a single round.
The victor progresses, but with the presence of heavy hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - judging by this showing - still looks steep.
Ricky Hatton Tribute Inspires Manchester Derby Fight
In the supporting bout, Arthur overcame Rea by close verdict in a terrific Manchester vs Manchester fight to capture the European light-heavyweight title.
The stadium grew hushed for a extremely emotional memorial ahead of the contest as ten bells tolled in remembrance of Manchester's own Hatton, who succumbed aged 46 in September.
It was the first major televised match card in the location since Hatton's passing. As the final chime faded, the silence gave way to a shout of "there's only one Hatton".
The fighting inside the ropes matched the emotion. Arthur was sent to the canvas by a powerful punch directly to the jaw in the early round, standing uncertainly to his feet on the count of eight.
But the red-colored shorts of Arthur soon advanced again. From the other corner, the opponent - in opposing blue - was injured quickly, heavy swelling forming under his face as the fighters exchanged hard punches.
The challenger, twenty-seven, connected with strong blows but the champion, 34, responded in kind with effective uppercuts as the pace rarely dropped over 12 rounds.
Arthur edged the result with judges scorecards of draw, close margin and clearer margin, but each competitor were persistent and brave, exactly what their idol the legend stood for.
