UK light-heavyweight Buatsi made a winning yet unimpressive start to his career under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a split decision in a competitive 10-round contest at the boxing arena.
But the challenger found success, connecting with powerful clean blows in a contest where the techniques didn't complement each other, with excessive holding marring the action.
The officials had it 96-94 for to Buatsi, with the final judge a even score.
"It wasn't my best showing but what defines champions? They prevail," Buatsi stated in the ring as he was greeted with disapproval from the spectators.
The British fighter bounced back after his initial pro loss - an epic battle with Callum Smith in February - to secure a 20th career victory.
Various analysts believed the challenger, 31, deserved the decision but the British boxer endured the second loss of his 28-match professional journey.
Buatsi Secures Victory in Uneventful Match
His career development has slowed in recent times through contract problems and considerable time of inactivity.
Previously predicted as the next star of UK boxing, he now is positioned trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under recent support.
He started carefully, with both competitors prepared to overcommit in a tentative early stages.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in two years ago after damaging his hand mid-fight, was participating in his second fight at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, making life awkward for the favorite, who utilized a protective stance to edge the better stanzas.
The crowd's patience wore thin during constant clinching, with Parker slipping to the canvas various instances during close exchanges.
The underdog finished the stronger, but several stanzas were difficult to score. However, ex-champion the boxing analyst - providing analysis for Dazn - had it significantly in favor for the challenger, scoring for Buatsi just one round.
The victor progresses, but with the caliber of hard hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the journey to titles - judging by this showing - still seems difficult.
Hatton Homage Motivates All-Manchester Contest
In the secondary fight, Arthur overcame Rea by close verdict in a outstanding Manchester vs Manchester battle to secure the European light heavyweight title.
The arena grew hushed for a deeply poignant memorial ahead of the contest as 10 bells sounded in honor of Manchester's own Hatton, who passed away aged 46 in recently.
It was the first major televised match card in the city since Hatton's passing. As the concluding sound disappeared, the silence became a chant of "only one Hatton".
The action within the ring matched the feeling. The eventual winner was floored by a left hook directly to the chin in the second round, getting up unsteadily to his footing on the eight count.
But the red-colored equipment of Arthur soon came forward again. From the other corner, Rea - in opposing blue - was injured quickly, heavy swelling appearing under his orbital area as the pair landed punishing blows.
Rea, 27, delivered effective strikes but the champion, thirty-four, responded in kind with powerful upward punches as the pace rarely dropped over 12 rounds.
The victor barely secured the decision with scoring tallies of even score, narrow lead and wider gap, but the two athletes were determined and full of heart, exactly what their inspiration the legend represented.
