UK light heavyweight Buatsi secured a victory yet disappointing beginning to his career under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output appeared to earn him a split decision in a competitive ten-round fight at the Co-op Live Arena.
But Parker landed significant shots, delivering effective individual punches in a fight where the styles failed to mesh, with frequent clinching marring the contest.
The officials judged it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my finest display but what do champions do? They prevail," the victor stated in the ring as he was met by disapproval from the crowd.
The British fighter got back to winning after his maiden career setback - an epic battle with Callum Smith in last winter - to secure a 20th career victory.
Some ringside observers believed Parker, 31, deserved the decision but the contender experienced the second setback of his 28-fight career.
The Champion Earns Triumph in Uneventful Affair
The fighter's advancement has plateaued in recent years through promotional disputes and considerable time of inactivity.
Earlier forecast as the next star of British boxing, he now is positioned trying to fulfil that early promise - maybe in what feels like a last chance - under new promotional backing.
He began cautiously, with the two boxers prepared to overcommit in a cagey initial rounds.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago after suffering a hand injury in the contest, was making just his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for the favorite, who worked behind a tight guard to edge the more effective periods.
The audience's tolerance wore thin amid constant clinching, with the challenger falling to the floor several times during grappling.
The underdog ended stronger, but multiple periods were challenging to assess. Nevertheless, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, giving Buatsi just only one stanza.
Buatsi progresses, but with the likes of hard hitter David Benavidez, and Russian star Bivol ruling the division, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Tribute Inspires All-Manchester Contest
In the secondary fight, Arthur defeated Rea by split-decision in a excellent local rivalry contest to capture the continental title.
The stadium grew hushed for a deeply poignant homage ahead of the contest as 10 bells sounded in memory of the city's native Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast boxing event in the city since Hatton's death. As the concluding sound ended, the silence transitioned to a roar of "only one Ricky Hatton".
The action inside the ropes matched the sentiment. The eventual winner was floored by a significant blow squarely on the jaw in the second round, rising shakily to his feet on the count of eight.
But the Manchester United-red shorts of Arthur soon advanced again. From the other corner, Rea - in competitive blue - was marked up early, heavy swelling forming under his eye as the fighters landed hard punches.
The challenger, 27, delivered effective strikes but the champion, thirty-four, fought fire with fire with effective uppercuts as the intensity seldom decreased over the full distance.
Arthur edged the result with official scores of even score, close margin and 115-112, but each competitor were relentless and brave, everything their hero Hatton embodied.
