British light heavyweight Buatsi earned a win yet unimpressive debut to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output likely gained him a majority decision in a close 10-round bout at the Manchester venue.
But Parker found success, landing some telling single shots in a match where the techniques never quite clicked, with excessive holding marring the contest.
The scoring judges had it 96-94 for to the winner, with the third a even score.
"It wasn't my best display but what defines champions? They succeed," Buatsi said in the arena as he was faced boos from the audience.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in last winter - to claim a twentieth professional win.
Various analysts felt Parker, thirty-one, deserved the win but the British boxer experienced the second loss of his 28-fight professional journey.
The Champion Secures Win in Slow Match
His career development has plateaued in recent years through management issues and considerable time of lack of fights.
Earlier forecast as the future of the British fight scene, he now is positioned trying to fulfil that early promise - perhaps in what appears to be a final roll of the dice - under new promotional backing.
He opened tentatively, with the two boxers prepared to take risks in a cagey early stages.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after damaging his hand mid-fight, was competing in only his second appearance at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, creating difficulties for Buatsi, who worked behind a solid defense to edge the cleaner stanzas.
The audience's tolerance decreased amid regular grabbing, with Parker going down several times during clinches.
The underdog finished the stronger, but multiple periods were hard to judge. However, previous titleholder Carl Frampton - commentating on Dazn - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
The victor moves on, but with the caliber of heavy hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Tribute Inspires Manchester Derby Battle
In the secondary fight, Arthur beat Rea by divided decision in a excellent local rivalry battle to capture the continental belt.
The stadium became quiet for a extremely emotional homage prior to the bout as a bell ceremony tolled in memory of local hero Ricky Hatton, who died aged 46 in September.
It was the first major televised boxing event in the location since Hatton's passing. As the concluding sound ended, the stillness gave way to a roar of "there's only one Hatton".
The competition inside the ropes reflected the emotion. Arthur was floored by a left hook directly to the jaw in the early round, rising shakily to his position on the referee's count.
But the traditional red equipment of the fighter soon advanced again. From the other corner, Rea - in rival City blue - was injured soon, noticeable damage appearing under his orbital area as the pair exchanged hard punches.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, fought fire with fire with effective uppercuts as the intensity hardly diminished over 12 rounds.
Arthur barely secured the result with scoring tallies of draw, 115-113 and wider gap, but each competitor were determined and courageous, all the qualities their idol Hatton represented.
