British light-heavyweight Buatsi earned a win yet underwhelming start to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a split decision in a competitive 10-round bout at the boxing arena.
But Parker had his moments, delivering effective individual punches in a match where the styles never quite clicked, with excessive holding spoiling the fight.
The officials judged it 96-94 to Buatsi, with the final judge a even score.
"It wasn't my finest showing but what defines champions? They prevail," the victor stated in the ring as he was greeted with boos from the crowd.
The British fighter got back to winning after his maiden career setback - an thrilling contest with his previous opponent in last winter - to earn a twentieth professional win.
Several boxing experts thought Parker, 31, deserved the victory but the British boxer endured the second loss of his 28-fight career.
Buatsi Secures Triumph in Uneventful Encounter
Buatsi's progress has stalled in recent years through management issues and considerable time of inactivity.
Earlier forecast as the next star of British boxing, he now stands trying to realize his potential - perhaps in what feels like a last chance - under fresh management.
He started carefully, with the two boxers willing to take risks in a cagey early stages.
Parker, whose sole prior loss came at the lower weight class against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second appearance at light-heavyweight.
By the middle rounds, the underdog had made it competitive, making life awkward for the favorite, who utilized a protective stance to narrowly win the better stanzas.
The audience's tolerance diminished because of regular grabbing, with the challenger falling to the floor several times during close exchanges.
Parker ended stronger, but multiple periods were challenging to assess. Nevertheless, ex-champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for Parker, awarding Buatsi just one round.
The victor progresses, but with the likes of power puncher David Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Hatton Homage Inspires Local Rivalry Contest
In the secondary fight, Arthur overcame Rea by split-decision in a terrific local rivalry fight to capture the European light-heavyweight championship.
The venue became quiet for a extremely emotional homage ahead of the contest as ten bells rang in memory of the city's native Ricky Hatton, who passed away aged 46 in September.
It was the first major televised boxing event in the urban center since Hatton's death. As the concluding sound ended, the silence gave way to a chant of "only one Hatton".
The fighting within the ring matched the emotion. The eventual winner was sent to the canvas by a powerful punch flush on the face in the early round, standing uncertainly to his footing on the count of eight.
But the traditional red attire of Arthur soon pressed ahead again. From the other corner, the opponent - in opposing blue - was injured early, noticeable damage forming under his face as the duo landed hard punches.
Rea, 27, delivered effective strikes but the champion, thirty-four, matched the intensity with stinging uppercuts as the action rarely dropped over twelve rounds.
Arthur barely secured the verdict with scoring tallies of draw, close margin and wider gap, but the two athletes were determined and full of heart, exactly what their hero Hatton stood for.
