UK light heavyweight Buatsi earned a win yet unimpressive debut to his career under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a split decision in a competitive 10-round fight at the Manchester venue.
But Parker had his moments, connecting with powerful clean blows in a match where the approaches failed to mesh, with frequent clinching disrupting the contest.
The officials had it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my greatest display but what do champions do? They prevail," Buatsi said in the arena as he was faced boos from the audience.
The Londoner bounced back after his initial pro loss - an memorable fight with Callum Smith in February - to secure a 20th pro success.
Several boxing experts felt the challenger, thirty-one, should have been awarded the victory but the British boxer experienced the second setback of his 28-match career.
The Champion Secures Triumph in Slow Encounter
His career development has stalled in recent times through contract problems and long spells of inactivity.
Once tipped as the next star of UK boxing, he now is positioned trying to achieve expectations - maybe in what feels like a final roll of the dice - under new promotional backing.
He opened tentatively, with neither fighter ready to take risks in a cagey opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after damaging his hand in the contest, was making just his second fight at light-heavyweight.
By the fight's midpoint, Parker had stayed in contention, making life awkward for Buatsi, who operated with a tight guard to narrowly win the cleaner stanzas.
The audience's tolerance diminished because of frequent holding, with the challenger slipping to the canvas various instances during clinches.
Parker finished the stronger, but multiple periods were challenging to assess. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it strongly leaning for the challenger, scoring for Buatsi just one round.
The victor advances, but with the presence of power puncher Benavidez, and Russian champion Bivol ruling the division, the journey to titles - on this evidence - still seems difficult.
Hatton Memorial Motivates Local Rivalry Battle
In the supporting bout, Arthur defeated Rea by divided decision in a outstanding local rivalry contest to win the continental belt.
The stadium became quiet for a profoundly moving homage prior to the bout as a bell ceremony tolled in memory of local hero Ricky Hatton, who died 46 years old in recently.
It was the initial significant broadcast fight night in the urban center since Hatton's death. As the concluding sound disappeared, the stillness gave way to a chant of "only one Hatton".
The competition inside the ropes reflected the feeling. Arthur was floored by a powerful punch squarely on the face in the initial stage, rising shakily to his feet on the eight count.
But the traditional red equipment of the fighter soon came forward again. On the opposite side, Rea - in opposing blue - was damaged soon, noticeable damage developing under his face as the duo traded powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with powerful upward punches as the intensity hardly diminished over the full distance.
The victor edged the decision with scoring tallies of draw, narrow lead and wider gap, but each competitor were determined and courageous, everything their inspiration Hatton embodied.
