UK light heavyweight Buatsi secured a victory yet unimpressive debut to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a split decision in a close ten-round contest at the boxing arena.
But the challenger landed significant shots, delivering effective single shots in a match where the approaches didn't complement each other, with excessive holding spoiling the contest.
The officials scored it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my best display but how do champions respond? They prevail," the victor stated in the ringside as he was met by negative reactions from the spectators.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in February - to secure a twentieth professional win.
Some ringside observers felt Parker, thirty-one, should have been awarded the win but the British boxer suffered the second loss of his 28-fight career.
Buatsi Claims Victory in Uneventful Encounter
The fighter's advancement has slowed in the past few years through contract problems and considerable time of lack of fights.
Earlier forecast as the future of British boxing, he now stands trying to fulfil that early promise - possibly in what seems like a last chance - under new promotional backing.
He opened tentatively, with the two boxers ready to overcommit in a tentative early stages.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in two years ago after suffering a hand injury during the bout, was making just his second appearance at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, making life awkward for Buatsi, who worked behind a protective stance to barely take the better periods.
The spectators' acceptance wore thin amid regular grabbing, with Parker going down multiple occasions during clinches.
The underdog closed well, but multiple periods were challenging to assess. However, former world champion Carl Frampton - working with Dazn - had it particularly wide for the challenger, scoring for Buatsi just a single round.
The victor moves on, but with the caliber of hard hitter David Benavidez, and Russian champion Bivol dominating the weight class, the path to championship success - based on this performance - still looks steep.
Hatton Homage Inspires Local Rivalry Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by split-decision in a outstanding local rivalry battle to win the European light heavyweight championship.
The stadium fell silent for a profoundly moving memorial ahead of the contest as ten bells tolled in memory of the city's native Ricky Hatton, who passed away aged 46 in September.
It was the initial significant broadcast match card in the urban center since Hatton's passing. As the last bell faded, the silence transitioned to a shout of "there's only one Ricky Hatton".
The competition inside the ropes equaled the sentiment. Arthur was sent to the canvas by a significant blow flush on the face in the early round, rising shakily to his feet on the referee's count.
But the traditional red equipment of the fighter soon pressed ahead again. From the other corner, Rea - in competitive blue - was injured quickly, heavy swelling appearing under his eye as the fighters traded punishing blows.
The challenger, twenty-seven, delivered effective strikes but Arthur, thirty-four, fought fire with fire with effective uppercuts as the action rarely dropped over twelve rounds.
The victor narrowly won the decision with scoring tallies of 114-114, narrow lead and 115-112, but the two athletes were determined and full of heart, exactly what their idol the legend embodied.
