British light heavyweight Buatsi secured a victory yet unimpressive debut to life under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's activity level likely gained him a split decision in a tight 10-round bout at the Manchester venue.
But the challenger had his moments, connecting with powerful individual punches in a fight where the approaches didn't complement each other, with frequent clinching spoiling the action.
The officials scored it 96-94 in favor to Buatsi, with the final judge a 95-95 draw.
"It wasn't my best display but what do champions do? They prevail," Buatsi commented in the ringside as he was greeted with boos from the spectators.
The British fighter returned to winning ways after his initial pro loss - an epic battle with his previous opponent in February - to earn a twentieth professional win.
Various analysts felt Parker, thirty-one, merited the decision but the contender endured the second setback of his 28-bout career.
The Champion Secures Win in Uneventful Affair
His career development has stalled in recent times through contract problems and considerable time of inactivity.
Previously predicted as the rising talent of the British fight scene, he now is positioned trying to achieve expectations - maybe in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors ready to overcommit in a calculated opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after breaking his hand during the bout, was participating in his second appearance at light heavyweight.
By the fight's midpoint, the underdog had stayed in contention, creating difficulties for the favorite, who worked behind a protective stance to narrowly win the more effective stanzas.
The spectators' acceptance wore thin during constant clinching, with the challenger slipping to the canvas several times during close exchanges.
The underdog finished the stronger, but several stanzas were difficult to score. However, former world champion Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter David Benavidez, and Russian star Bivol leading the category, the road to world glory - judging by this showing - still looks steep.
Hatton Tribute Inspires Local Rivalry Contest
In the secondary fight, Lyndon Arthur overcame Rea by divided decision in a outstanding Manchester vs Manchester contest to win the continental belt.
The arena became quiet for a deeply poignant memorial ahead of the contest as a bell ceremony rang in memory of local hero Ricky Hatton, who passed away at age 46 in last month.
It was the initial significant broadcast match card in the city since Hatton's passing. As the concluding sound ended, the stillness became a chant of "there's just one Ricky Hatton".
The competition inside the ropes equaled the feeling. Arthur was knocked down by a left hook squarely on the face in the early round, standing uncertainly to his footing on the eight count.
But the Manchester United-red equipment of the fighter soon pressed ahead again. From the other corner, the opponent - in competitive blue - was damaged early, noticeable damage forming under his face as the duo exchanged powerful shots.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, fought fire with fire with effective uppercuts as the intensity seldom decreased over twelve rounds.
The victor barely secured the verdict with judges scorecards of even score, narrow lead and 115-112, but both fighters were relentless and full of heart, exactly what their hero the legend embodied.
