British light heavyweight Buatsi made a winning yet disappointing start to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a split decision in a tight ten-round bout at the Manchester venue.
But Parker had his moments, connecting with powerful clean blows in a contest where the techniques didn't complement each other, with frequent clinching spoiling the fight.
The scoring judges scored it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my greatest performance but what defines champions? They win," Buatsi said in the ring as he was greeted with negative reactions from the spectators.
The Londoner returned to winning ways after his maiden career setback - an epic battle with his previous opponent in last winter - to earn a twentieth professional win.
Several boxing experts thought Parker, 31, merited the decision but the contender suffered the second setback of his 28-match career.
The Champion Claims Victory in Uneventful Affair
The fighter's advancement has slowed in the past few years through management issues and long spells of lack of fights.
Once tipped as the next star of UK boxing, he now finds himself trying to achieve expectations - maybe in what seems like a last chance - under new promotional backing.
He started carefully, with neither fighter ready to be aggressive in a calculated early stages.
The challenger, whose single earlier setback came at super middleweight against his former opponent in two years ago after damaging his hand in the contest, was participating in his second appearance at light-heavyweight.
By the middle rounds, Parker had made it competitive, creating difficulties for Buatsi, who utilized a solid defense to edge the more effective stanzas.
The crowd's patience decreased amid regular grabbing, with Parker slipping to the canvas several times during clinches.
Parker closed well, but several stanzas were hard to judge. Nevertheless, former world champion Carl Frampton - working with Dazn - had it particularly wide for Parker, scoring for Buatsi just one round.
Buatsi advances, but with the presence of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - on this evidence - still looks steep.
Ricky Hatton Homage Motivates Manchester Derby Contest
In the co-main event, Arthur overcame Bradley Rea by close verdict in a excellent all-Manchester fight to capture the European light-heavyweight title.
The stadium fell silent for a profoundly moving homage ahead of the contest as a bell ceremony sounded in honor of the city's native Ricky Hatton, who passed away aged 46 in September.
It was the initial significant broadcast boxing event in the location since Hatton's passing. As the last bell ended, the stillness transitioned to a shout of "there's only one Hatton".
The competition inside the ropes reflected the feeling. Arthur was knocked down by a powerful punch flush on the face in the initial stage, rising shakily to his position on the referee's count.
But the red-colored shorts of the fighter soon came forward again. Across the ring, Rea - in competitive blue - was injured early, noticeable damage appearing under his orbital area as the duo exchanged powerful shots.
The challenger, 27, connected with strong blows but the champion, thirty-four, matched the intensity with stinging uppercuts as the pace seldom decreased over twelve rounds.
Arthur edged the decision with scoring tallies of 114-114, 115-113 and clearer margin, but each competitor were relentless and brave, exactly what their idol Hatton stood for.
