British light-heavyweight Buatsi made a winning yet disappointing beginning to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a close 10-round fight at the Manchester venue.
But Parker landed significant shots, connecting with powerful individual punches in a contest where the techniques never quite clicked, with constant grabbing spoiling the action.
Two judges had it 96-94 to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest showing but what defines champions? They win," Buatsi commented in the arena as he was met by boos from the spectators.
The Londoner got back to winning after his initial pro loss - an thrilling contest with his previous opponent in February - to earn a twentieth professional win.
Several boxing experts believed Parker, thirty-one, merited the victory but the British boxer experienced the second setback of his 28-match professional journey.
The Champion Secures Victory in Uneventful Match
The fighter's advancement has plateaued in recent times through contract problems and long spells of lack of fights.
Previously predicted as the future of British boxing, he now finds himself trying to realize his potential - maybe in what appears to be a last chance - under recent support.
He started carefully, with the two boxers willing to take risks in a cagey initial rounds.
Parker, whose sole prior loss came at super-middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was participating in his second appearance at the higher weight class.
By the halfway stage, Parker had stayed in contention, creating difficulties for Buatsi, who operated with a tight guard to barely take the cleaner rounds.
The spectators' acceptance wore thin because of constant clinching, with the challenger slipping to the canvas several times during clinches.
Parker closed well, but many rounds were difficult to score. However, former world champion the boxing analyst - providing analysis for Dazn - had it particularly wide for Parker, awarding Buatsi just a single round.
Buatsi moves on, but with the likes of hard hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - on this evidence - still appears challenging.
Hatton Tribute Inspires Local Rivalry Fight
In the secondary fight, Arthur defeated Rea by split-decision in a excellent Manchester vs Manchester battle to capture the European light-heavyweight championship.
The stadium fell silent for a profoundly moving memorial ahead of the contest as ten bells sounded in memory of Manchester's own Hatton, who died aged 46 in recently.
It was the initial significant broadcast match card in the location since the passing of Hatton. As the concluding sound faded, the silence gave way to a shout of "there's just one Ricky Hatton".
The fighting inside the ropes equaled the feeling. Arthur was sent to the canvas by a left hook flush on the chin in the initial stage, getting up unsteadily to his position on the referee's count.
But the red-colored attire of Arthur soon pressed ahead again. From the other corner, Rea - in competitive blue - was marked up early, significant bruising appearing under his face as the pair landed powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with powerful upward punches as the pace seldom decreased over 12 rounds.
The victor edged the verdict with official scores of 114-114, close margin and wider gap, but the two athletes were relentless and brave, exactly what their idol Hatton embodied.
