UK light-heavyweight Buatsi made a winning yet disappointing debut to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a judges' verdict in a close ten-round bout at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful clean blows in a contest where the approaches failed to mesh, with constant grabbing disrupting the action.
Two judges judged it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest performance but what defines champions? They succeed," Buatsi commented in the ring as he was faced negative reactions from the crowd.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with his previous opponent in last winter - to secure a 20th career victory.
Several boxing experts felt Parker, 31, should have been awarded the victory but the Derbyshire fighter suffered the second setback of his 28-bout professional journey.
The Champion Claims Win in Uneventful Affair
Buatsi's progress has stalled in recent years through contract problems and extended periods of lack of fights.
Earlier forecast as the future of British boxing, he now finds himself trying to achieve expectations - perhaps in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with both competitors ready to take risks in a calculated opening few rounds.
Parker, whose sole prior loss came at super-middleweight against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second appearance at light heavyweight.
By the halfway stage, Parker had made it competitive, creating difficulties for Buatsi, who utilized a solid defense to barely take the cleaner periods.
The spectators' acceptance diminished amid frequent holding, with the challenger slipping to the canvas multiple occasions during clinches.
Parker finished the stronger, but many rounds were hard to judge. Nevertheless, former world champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for the challenger, giving Buatsi just one round.
The victor progresses, but with the caliber of power puncher David Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - judging by this showing - still seems difficult.
Hatton Tribute Fuels Local Rivalry Battle
In the secondary fight, Arthur beat Rea by divided decision in a terrific local rivalry contest to win the European light-heavyweight championship.
The arena became quiet for a profoundly moving homage before the fight as a bell ceremony sounded in remembrance of local hero Ricky Hatton, who succumbed aged 46 in September.
It was the initial significant broadcast match card in the urban center since Hatton's passing. As the final chime faded, the stillness became a shout of "only one Hatton".
The action during the bout equaled the emotion. The eventual winner was knocked down by a powerful punch directly to the chin in the second round, getting up unsteadily to his feet on the count of eight.
But the traditional red attire of the fighter soon advanced again. Across the ring, Rea - in rival City blue - was damaged soon, significant bruising forming under his eye as the pair landed punishing blows.
Rea, 27, connected with strong blows but the champion, 34, fought fire with fire with stinging uppercuts as the pace hardly diminished over twelve rounds.
The victor barely secured the decision with official scores of draw, narrow lead and wider gap, but each competitor were relentless and courageous, everything their hero the legend represented.
