UK light heavyweight Buatsi made a winning yet underwhelming beginning to life under recent management with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a close 10-round fight at the boxing arena.
But Parker had his moments, landing some telling single shots in a contest where the styles never quite clicked, with excessive holding marring the contest.
The officials judged it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my greatest showing but how do champions respond? They succeed," the victor stated in the ring as he was faced boos from the audience.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with Callum Smith in February - to secure a 20th career victory.
Several boxing experts felt the challenger, thirty-one, deserved the win but the contender suffered the second defeat of his 28-bout professional journey.
The Champion Earns Win in Dull Match
Buatsi's progress has plateaued in recent years through contract problems and considerable time of inactivity.
Earlier forecast as the future of UK boxing, he now stands trying to realize his potential - maybe in what seems like a last chance - under fresh management.
He began cautiously, with both competitors prepared to be aggressive in a calculated opening few rounds.
The challenger, whose single earlier setback came at super middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was competing in only his second fight at the higher weight class.
By the middle rounds, Parker had stayed in contention, making life awkward for the favorite, who operated with a tight guard to edge the cleaner rounds.
The audience's tolerance decreased during frequent holding, with the challenger slipping to the canvas multiple occasions during grappling.
Parker closed well, but multiple periods were hard to judge. Nevertheless, ex-champion the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
The victor moves on, but with the presence of heavy hitter David Benavidez, and Eastern European fighter Bivol dominating the weight class, the path to championship success - on this evidence - still seems difficult.
Hatton Memorial Fuels Manchester Derby Battle
In the co-main event, Arthur overcame Rea by split-decision in a terrific local rivalry battle to capture the European light heavyweight title.
The venue became quiet for a deeply poignant tribute ahead of the contest as ten bells sounded in honor of the city's native Ricky Hatton, who passed away at age 46 in recently.
It was the first major televised match card in the urban center since Hatton's death. As the concluding sound ended, the stillness transitioned to a roar of "only one Hatton".
The action within the ring equaled the sentiment. The eventual winner was floored by a significant blow directly to the jaw in the second round, getting up unsteadily to his position on the count of eight.
But the traditional red equipment of the fighter soon advanced again. From the other corner, the opponent - in opposing blue - was injured soon, significant bruising forming under his face as the fighters traded hard punches.
Rea, twenty-seven, connected with strong blows but the champion, 34, responded in kind with powerful upward punches as the pace rarely dropped over 12 rounds.
Arthur narrowly won the verdict with official scores of even score, close margin and 115-112, but each competitor were persistent and brave, exactly what their hero the legend stood for.
