UK light heavyweight Buatsi made a winning yet unimpressive debut to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a split decision in a competitive 10-round contest at the boxing arena.
But Parker found success, connecting with powerful individual punches in a fight where the approaches failed to mesh, with constant grabbing marring the action.
The officials had it 96-94 to the winner, with the third a 95-95 draw.
"It wasn't my greatest performance but what do champions do? They succeed," Buatsi stated in the ring as he was met by boos from the crowd.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in last winter - to claim a 20th pro success.
Various analysts believed the challenger, 31, deserved the decision but the Derbyshire fighter suffered the second defeat of his 28-fight professional journey.
Buatsi Secures Win in Dull Match
His career development has stalled in recent years through contract problems and long spells of lack of fights.
Earlier forecast as the future of the British fight scene, he now finds himself trying to achieve expectations - possibly in what feels like a last chance - under fresh management.
He started carefully, with neither fighter ready to overcommit in a tentative early stages.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after damaging his hand in the contest, was participating in his second appearance at the higher weight class.
By the middle rounds, Parker had made it competitive, causing problems for Buatsi, who utilized a solid defense to edge the cleaner stanzas.
The crowd's patience diminished because of constant clinching, with the challenger slipping to the canvas multiple occasions during close exchanges.
The underdog finished the stronger, but many rounds were difficult to score. Although, former world champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just one round.
Buatsi advances, but with the likes of heavy hitter David Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Homage Motivates Manchester Derby Contest
In the supporting bout, Lyndon Arthur beat Bradley Rea by split-decision in a outstanding local rivalry battle to capture the European light heavyweight championship.
The stadium became quiet for a extremely emotional tribute ahead of the contest as a bell ceremony tolled in remembrance of the city's native Hatton, who died at age 46 in last month.
It was the initial significant broadcast match card in the city since the passing of Hatton. As the concluding sound faded, the stillness transitioned to a chant of "there's only one Hatton".
The competition during the bout reflected the emotion. Arthur was sent to the canvas by a left hook flush on the jaw in the initial stage, getting up unsteadily to his footing on the referee's count.
But the red-colored shorts of Arthur soon pressed ahead again. Across the ring, Rea - in opposing blue - was damaged soon, noticeable damage developing under his orbital area as the duo traded punishing blows.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, fought fire with fire with effective uppercuts as the pace seldom decreased over the full distance.
Arthur barely secured the decision with judges scorecards of draw, narrow lead and clearer margin, but the two athletes were determined and courageous, exactly what their idol the legend represented.
