British light heavyweight Buatsi made a winning yet unimpressive debut to his career under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a majority decision in a competitive ten-round bout at the Co-op Live Arena.
But the challenger found success, connecting with powerful individual punches in a contest where the techniques never quite clicked, with constant grabbing disrupting the action.
The scoring judges had it 96-94 in favor to the winner, with the third a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They prevail," Buatsi commented in the arena as he was met by negative reactions from the audience.
The British fighter returned to winning ways after his first professional defeat - an epic battle with Callum Smith in last winter - to secure a 20th career victory.
Several boxing experts thought the challenger, thirty-one, deserved the victory but the contender experienced the second setback of his 28-match professional journey.
Buatsi Claims Win in Dull Affair
His career development has stalled in the past few years through promotional disputes and long spells of lack of fights.
Previously predicted as the rising talent of the British fight scene, he now finds himself trying to fulfil that early promise - perhaps in what appears to be a last chance - under recent support.
He began cautiously, with neither fighter prepared to overcommit in a tentative initial rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after breaking his hand mid-fight, was making just his second bout at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, creating difficulties for the favorite, who worked behind a solid defense to narrowly win the better periods.
The crowd's patience wore thin amid frequent holding, with Parker going down several times during clinches.
The underdog finished the stronger, but many rounds were challenging to assess. Although, former world champion the boxing analyst - working with Dazn - had it strongly leaning for Parker, awarding Buatsi just a single round.
Buatsi advances, but with the presence of hard hitter David Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Homage Inspires Manchester Derby Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by divided decision in a excellent all-Manchester fight to capture the European light heavyweight title.
The arena grew hushed for a deeply poignant tribute prior to the bout as 10 bells rang in remembrance of Manchester's own Hatton, who passed away aged 46 in recently.
It was the first major televised boxing event in the city since Hatton's death. As the last bell faded, the silence transitioned to a chant of "there's only one Hatton".
The fighting inside the ropes matched the sentiment. The eventual winner was knocked down by a significant blow flush on the face in the second round, rising shakily to his footing on the referee's count.
But the Manchester United-red attire of the fighter soon came forward again. From the other corner, the opponent - in competitive blue - was marked up soon, significant bruising forming under his face as the pair traded punishing blows.
The challenger, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with stinging uppercuts as the pace rarely dropped over the full distance.
Arthur barely secured the result with judges scorecards of draw, close margin and wider gap, but each competitor were persistent and full of heart, all the qualities their inspiration the legend embodied.
