UK light-heavyweight Buatsi made a winning yet disappointing beginning to his career under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's activity level likely gained him a split decision in a close ten-round contest at the boxing arena.
But Parker found success, delivering effective individual punches in a contest where the styles never quite clicked, with excessive holding disrupting the contest.
The officials judged it 96-94 for to the winner, with the third a even score.
"It wasn't my finest performance but what defines champions? They prevail," the victor said in the ring as he was faced disapproval from the spectators.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Several boxing experts believed Parker, 31, merited the victory but the contender experienced the second setback of his 28-match career.
The Champion Claims Triumph in Slow Match
His career development has stalled in the past few years through management issues and extended periods of lack of fights.
Previously predicted as the rising talent of the British fight scene, he now is positioned trying to achieve expectations - perhaps in what appears to be a final roll of the dice - under new promotional backing.
He started carefully, with both competitors willing to be aggressive in a calculated opening few rounds.
Parker, whose sole prior loss came at super middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was participating in his second fight at light-heavyweight.
By the middle rounds, the underdog had stayed in contention, causing problems for the favorite, who operated with a protective stance to narrowly win the more effective rounds.
The spectators' acceptance wore thin during regular grabbing, with Parker going down various instances during grappling.
Parker finished the stronger, but many rounds were difficult to score. Nevertheless, ex-champion the boxing analyst - providing analysis for Dazn - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the presence of hard hitter David Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Tribute Fuels Manchester Derby Contest
In the secondary fight, Arthur beat Bradley Rea by split-decision in a excellent Manchester vs Manchester fight to win the European light heavyweight championship.
The arena became quiet for a profoundly moving tribute ahead of the contest as 10 bells sounded in remembrance of Manchester's own Hatton, who passed away at age 46 in last month.
It was the first major televised fight night in the city since Hatton's death. As the final chime ended, the silence became a shout of "only one Hatton".
The action within the ring reflected the emotion. The eventual winner was sent to the canvas by a powerful punch squarely on the face in the initial stage, standing uncertainly to his footing on the eight count.
But the Manchester United-red attire of the fighter soon came forward again. Across the ring, Rea - in competitive blue - was damaged quickly, significant bruising appearing under his orbital area as the duo landed powerful shots.
The challenger, 27, delivered effective strikes but the champion, thirty-four, responded in kind with powerful upward punches as the intensity rarely dropped over 12 rounds.
Arthur narrowly won the decision with scoring tallies of even score, close margin and wider gap, but each competitor were determined and full of heart, everything their idol the legend stood for.
