UK light heavyweight Buatsi earned a win yet underwhelming beginning to his career under new promoters with a decision win over Parker in Manchester.
The Olympic medal winner's punch output likely gained him a majority decision in a competitive ten-round fight at the Manchester venue.
But the challenger found success, connecting with powerful individual punches in a fight where the styles failed to mesh, with constant grabbing spoiling the action.
Two judges had it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my finest display but what do champions do? They prevail," Buatsi stated in the arena as he was faced negative reactions from the spectators.
The British fighter bounced back after his initial pro loss - an epic battle with his previous opponent in last winter - to earn a 20th career victory.
Various analysts felt the challenger, 31, deserved the victory but the Derbyshire fighter suffered the second setback of his 28-fight professional journey.
Buatsi Earns Win in Dull Affair
Buatsi's progress has plateaued in the past few years through contract problems and considerable time of lack of fights.
Once tipped as the next star of the British fight scene, he now stands trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with neither fighter prepared to take risks in a tentative initial rounds.
Parker, whose sole prior loss came at super middleweight against John Ryder in two years ago after damaging his hand during the bout, was participating in his second bout at light-heavyweight.
By the halfway stage, Parker had stayed in contention, making life awkward for the favorite, who worked behind a protective stance to edge the better rounds.
The crowd's patience diminished amid regular grabbing, with the challenger falling to the floor various instances during clinches.
Parker ended stronger, but multiple periods were hard to judge. However, previous titleholder the boxing analyst - working with Dazn - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
Buatsi progresses, but with the presence of power puncher David Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Ricky Hatton Tribute Motivates All-Manchester Battle
In the secondary fight, Lyndon Arthur overcame Bradley Rea by divided decision in a outstanding all-Manchester fight to capture the European light heavyweight championship.
The stadium grew hushed for a profoundly moving homage prior to the bout as 10 bells tolled in memory of the city's native Hatton, who succumbed aged 46 in September.
It was the initial significant broadcast boxing event in the urban center since Hatton's passing. As the last bell disappeared, the silence transitioned to a shout of "there's just one Ricky Hatton".
The action within the ring equaled the feeling. Arthur was sent to the canvas by a left hook squarely on the face in the initial stage, getting up unsteadily to his footing on the count of eight.
But the Manchester United-red shorts of the fighter soon pressed ahead again. Across the ring, Rea - in competitive blue - was injured quickly, significant bruising appearing under his face as the pair landed hard punches.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, responded in kind with stinging uppercuts as the pace seldom decreased over twelve rounds.
Arthur barely secured the decision with official scores of 114-114, close margin and wider gap, but each competitor were determined and courageous, exactly what their hero the legend represented.
