UK light heavyweight Buatsi made a winning yet unimpressive start to his career under recent management with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a split decision in a close 10-round bout at the boxing arena.
But Parker found success, delivering effective clean blows in a fight where the techniques didn't complement each other, with constant grabbing disrupting the action.
The officials judged it 96-94 to Buatsi, with the third a even score.
"It wasn't my finest display but what do champions do? They prevail," the victor said in the ring as he was greeted with boos from the crowd.
The Londoner got back to winning after his initial pro loss - an epic battle with Callum Smith in February - to earn a twentieth professional win.
Several boxing experts thought Parker, thirty-one, merited the decision but the British boxer suffered the second setback of his 28-fight career.
Buatsi Claims Triumph in Slow Encounter
His career development has stalled in recent years through management issues and considerable time of lack of fights.
Previously predicted as the next star of the British fight scene, he now finds himself trying to realize his potential - perhaps in what appears to be a final roll of the dice - under recent support.
He started carefully, with both competitors prepared to overcommit in a calculated initial rounds.
The challenger, whose single earlier setback came at super middleweight against his former opponent in 2022 after breaking his hand during the bout, was making just his second fight at light heavyweight.
By the halfway stage, the underdog had kept it close, creating difficulties for the favorite, who worked behind a solid defense to edge the more effective rounds.
The audience's tolerance diminished because of frequent holding, with Parker going down several times during grappling.
Parker finished the stronger, but several stanzas were challenging to assess. Although, previous titleholder Carl Frampton - providing analysis for Dazn - had it particularly wide for the challenger, awarding Buatsi just one round.
Buatsi advances, but with the presence of heavy hitter David Benavidez, and Russian star Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still seems difficult.
Ricky Hatton Tribute Inspires Manchester Derby Contest
In the secondary fight, Arthur overcame Bradley Rea by close verdict in a outstanding local rivalry contest to secure the continental belt.
The arena grew hushed for a extremely emotional memorial ahead of the contest as a bell ceremony rang in honor of the city's native Ricky Hatton, who passed away at age 46 in recently.
It was the premier televised match card in the urban center since the passing of Hatton. As the last bell disappeared, the silence became a roar of "there's only one Hatton".
The action during the bout matched the feeling. The eventual winner was knocked down by a powerful punch squarely on the face in the initial stage, rising shakily to his feet on the referee's count.
But the traditional red equipment of Arthur soon pressed ahead again. On the opposite side, Rea - in competitive blue - was marked up quickly, significant bruising forming under his eye as the duo traded powerful shots.
Rea, twenty-seven, landed power punches but the champion, thirty-four, matched the intensity with stinging uppercuts as the intensity hardly diminished over twelve rounds.
Arthur narrowly won the result with scoring tallies of 114-114, 115-113 and wider gap, but each competitor were relentless and full of heart, everything their inspiration Hatton stood for.
