UK light heavyweight Buatsi earned a win yet unimpressive start to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a judges' verdict in a close ten-round contest at the Manchester venue.
But the challenger found success, connecting with powerful single shots in a match where the styles never quite clicked, with excessive holding marring the fight.
Two judges judged it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my greatest showing but what defines champions? They succeed," the victor stated in the ringside as he was met by disapproval from the spectators.
The British fighter bounced back after his maiden career setback - an memorable fight with his previous opponent in February - to claim a 20th pro success.
Some ringside observers thought Parker, thirty-one, deserved the victory but the Derbyshire fighter endured the second setback of his 28-bout professional journey.
The Champion Earns Triumph in Dull Affair
His career development has plateaued in recent years through management issues and considerable time of inactivity.
Previously predicted as the future of the British fight scene, he now is positioned trying to realize his potential - possibly in what appears to be a final roll of the dice - under fresh management.
He started carefully, with neither fighter prepared to take risks in a tentative early stages.
Parker, whose only previous defeat came at the lower weight class against his former opponent in 2022 after breaking his hand mid-fight, was competing in only his second bout at light-heavyweight.
By the middle rounds, the underdog had stayed in contention, making life awkward for the favorite, who operated with a protective stance to edge the better stanzas.
The audience's tolerance decreased because of regular grabbing, with the challenger slipping to the canvas several times during clinches.
Parker closed well, but multiple periods were hard to judge. Although, ex-champion Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, giving Buatsi just only one stanza.
The victor moves on, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still seems difficult.
Hatton Tribute Fuels Local Rivalry Contest
In the supporting bout, Arthur defeated Rea by close verdict in a terrific Manchester vs Manchester battle to win the continental championship.
The arena fell silent for a extremely emotional memorial prior to the bout as a bell ceremony sounded in remembrance of the city's native Ricky Hatton, who died 46 years old in last month.
It was the premier televised fight night in the location since Hatton's passing. As the final chime faded, the stillness gave way to a chant of "there's just one Ricky Hatton".
The competition during the bout matched the emotion. The eventual winner was knocked down by a powerful punch directly to the chin in the second round, rising shakily to his footing on the referee's count.
But the red-colored shorts of Arthur soon came forward again. From the other corner, Rea - in competitive blue - was injured quickly, significant bruising forming under his eye as the duo landed punishing blows.
Rea, 27, connected with strong blows but the champion, 34, responded in kind with stinging uppercuts as the intensity seldom decreased over the full distance.
Arthur edged the verdict with judges scorecards of draw, close margin and wider gap, but each competitor were relentless and courageous, exactly what their idol Hatton represented.
