UK light heavyweight Buatsi made a winning yet disappointing debut to life under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate appeared to earn him a judges' verdict in a tight 10-round bout at the Co-op Live Arena.
But the challenger found success, delivering effective single shots in a contest where the approaches never quite clicked, with constant grabbing spoiling the fight.
The officials judged it 96-94 for to Buatsi, with the third a even score.
"It wasn't my finest performance but how do champions respond? They succeed," Buatsi commented in the arena as he was greeted with boos from the audience.
The Londoner got back to winning after his first professional defeat - an memorable fight with his previous opponent in February - to claim a twentieth professional win.
Several boxing experts felt Parker, 31, deserved the victory but the contender experienced the second setback of his 28-bout career.
The Champion Claims Triumph in Uneventful Match
His career development has slowed in recent years through management issues and extended periods of lack of fights.
Previously predicted as the future of UK boxing, he now stands trying to realize his potential - perhaps in what appears to be a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter willing to overcommit in a calculated 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 in the contest, was making just his second fight at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for Buatsi, who operated with a tight guard to barely take the cleaner periods.
The spectators' acceptance wore thin during regular grabbing, with the challenger falling to the floor several times during clinches.
Parker closed well, but many rounds were hard to judge. Although, previous titleholder the boxing analyst - working with Dazn - had it particularly wide for Parker, awarding Buatsi just one round.
Buatsi advances, but with the presence of power puncher Benavidez, and Russian star Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Tribute Inspires All-Manchester Contest
In the secondary fight, Arthur beat Bradley Rea by divided decision in a excellent local rivalry battle to capture the European light heavyweight title.
The arena became quiet for a deeply poignant memorial ahead of the contest as ten bells tolled in memory of local hero Ricky Hatton, who died aged 46 in recently.
It was the initial significant broadcast match card in the urban center since the passing of Hatton. As the last bell ended, the silence gave way to a chant of "there's just one Hatton".
The fighting within the ring equaled the feeling. The eventual winner was knocked down by a significant blow flush on the chin in the initial stage, getting up unsteadily to his footing on the count of eight.
But the Manchester United-red attire of the fighter soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was marked up quickly, significant bruising developing under his eye as the fighters exchanged powerful shots.
The challenger, 27, connected with strong blows but the champion, 34, fought fire with fire with effective uppercuts as the intensity hardly diminished over the full distance.
The victor edged the decision with scoring tallies of even score, narrow lead and wider gap, but the two athletes were determined and full of heart, all the qualities their inspiration the legend embodied.
