British light-heavyweight Buatsi made a winning yet unimpressive beginning to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a split decision in a close 10-round fight at the Manchester venue.
But Parker found success, landing some telling individual punches in a fight where the approaches failed to mesh, with frequent clinching spoiling the action.
The officials scored it 96-94 to the winner, with the final judge a 95-95.
"It wasn't my greatest showing but what defines champions? They succeed," the victor said in the ringside as he was met by boos from the spectators.
The British fighter bounced back after his initial pro loss - an epic battle with his previous opponent in February - to earn a 20th pro success.
Several boxing experts thought the challenger, 31, deserved the victory but the Derbyshire fighter experienced the second loss of his 28-match professional journey.
The Champion Earns Triumph in Slow Affair
His career development has plateaued in recent years through management issues and considerable time of inactivity.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to fulfil that early promise - perhaps in what appears to be a last chance - under fresh management.
He opened tentatively, with the two boxers ready to overcommit in a calculated opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in 2022 after suffering a hand injury mid-fight, was competing in only his second fight at light heavyweight.
By the middle rounds, Parker had kept it close, causing problems for Buatsi, who operated with a solid defense to narrowly win the more effective periods.
The spectators' acceptance wore thin during regular grabbing, with the challenger falling to the floor several times during grappling.
Parker ended stronger, but several stanzas were difficult to score. Although, ex-champion the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
The victor advances, but with the likes of power puncher David Benavidez, and Russian champion Bivol ruling the division, the road to world glory - based on this performance - still appears challenging.
Hatton Homage Motivates All-Manchester Battle
In the secondary fight, Arthur beat Rea by close verdict in a terrific Manchester vs Manchester battle to win the European light-heavyweight belt.
The arena grew hushed for a extremely emotional tribute ahead of the contest as ten bells rang in honor of local hero Ricky Hatton, who succumbed at age 46 in last month.
It was the premier televised match card in the city since Hatton's death. As the concluding sound ended, the stillness gave way to a shout of "only one Ricky Hatton".
The fighting during the bout matched the feeling. Arthur was sent to the canvas by a significant blow flush on the jaw in the second round, getting up unsteadily to his feet on the referee's count.
But the Manchester United-red attire of the fighter soon advanced again. Across the ring, the opponent - in opposing blue - was damaged soon, heavy swelling appearing under his face as the duo exchanged powerful shots.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, matched the intensity with powerful upward punches as the pace hardly diminished over twelve rounds.
The victor edged the result with scoring tallies of draw, close margin and wider gap, but both fighters were determined and full of heart, all the qualities their inspiration the legend stood for.
