UK light heavyweight Buatsi secured a victory yet unimpressive debut to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a competitive ten-round fight at the Co-op Live Arena.
But Parker found success, connecting with powerful individual punches in a match where the techniques never quite clicked, with excessive holding marring the contest.
Two judges judged it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my best showing but what do champions do? They win," Buatsi commented in the ringside as he was met by negative reactions from the spectators.
The British fighter got back to winning after his first professional defeat - an epic battle with Callum Smith in February - to secure a 20th pro success.
Several boxing experts believed Parker, 31, should have been awarded the win but the contender suffered the second defeat of his 28-fight professional journey.
The Champion Earns Triumph in Dull Affair
Buatsi's progress has slowed in recent times through management issues and extended periods of lack of fights.
Once tipped as the rising talent of British boxing, he now is positioned trying to achieve expectations - possibly in what appears to be a last chance - under new promotional backing.
He started carefully, with the two boxers ready to overcommit in a calculated early stages.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in two years ago after damaging his hand in the contest, was competing in only his second fight at light heavyweight.
By the fight's midpoint, 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 diminished because of frequent holding, with Parker going down various instances during close exchanges.
The underdog finished the stronger, but multiple periods were challenging to assess. Although, previous titleholder the boxing analyst - providing analysis for Dazn - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
Buatsi progresses, but with the likes of power puncher David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still appears challenging.
Hatton Memorial Fuels Manchester Derby Contest
In the co-main event, Arthur overcame Bradley Rea by divided decision in a terrific Manchester vs Manchester contest to win the European light-heavyweight belt.
The arena became quiet for a profoundly moving tribute ahead of the contest as ten bells sounded in remembrance of the city's native Hatton, who died 46 years old in recently.
It was the first major televised boxing event in the urban center since Hatton's passing. As the last bell disappeared, the silence became a shout of "only one Hatton".
The competition during the bout matched the feeling. The eventual winner was floored by a powerful punch flush on the jaw in the initial stage, rising shakily to his feet on the count of eight.
But the Manchester United-red equipment of Arthur soon came forward again. Across the ring, Rea - in competitive blue - was damaged soon, noticeable damage forming under his orbital area as the duo exchanged powerful shots.
The challenger, 27, delivered effective strikes but the champion, thirty-four, responded in kind with stinging uppercuts as the pace seldom decreased over twelve rounds.
Arthur barely secured the verdict with official scores of 114-114, close margin and clearer margin, but both fighters were persistent and full of heart, everything their hero the legend stood for.
