British light heavyweight Buatsi earned a win yet underwhelming beginning to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a tight 10-round contest at the Co-op Live Arena.
But the challenger found success, landing some telling single shots in a contest where the styles didn't complement each other, with frequent clinching disrupting the action.
The officials had it 96-94 to the winner, with the final judge a 95-95.
"It wasn't my greatest performance but what do champions do? They prevail," the victor said in the ringside as he was met by disapproval from the spectators.
The Londoner bounced back after his first professional defeat - an memorable fight with his previous opponent in February - to earn a twentieth professional win.
Several boxing experts felt Parker, 31, deserved the victory but the British boxer endured the second defeat of his 28-fight professional journey.
Buatsi Claims Win in Dull Match
The fighter's advancement has plateaued in the past few years through management issues and considerable time of inactivity.
Once tipped as the future of British boxing, he now finds himself trying to realize his potential - possibly in what seems like a last chance - under new promotional backing.
He began cautiously, with both competitors ready to be aggressive in a cagey initial rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after damaging his hand during the bout, was making just his second fight at light-heavyweight.
By the halfway stage, Parker had made it competitive, creating difficulties for the favorite, who worked behind a protective stance to narrowly win the cleaner periods.
The audience's tolerance decreased because of frequent holding, with Parker falling to the floor various instances during clinches.
Parker ended stronger, but multiple periods were difficult to score. However, ex-champion Carl Frampton - providing analysis for Dazn - had it particularly wide for Parker, scoring for Buatsi just a single round.
Buatsi progresses, but with the caliber of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - on this evidence - still seems difficult.
Hatton Memorial Motivates Manchester Derby Fight
In the supporting bout, Arthur overcame Rea by split-decision in a outstanding local rivalry battle to capture the European light-heavyweight title.
The arena fell silent for a deeply poignant homage before the fight as ten bells sounded in memory of local hero Ricky Hatton, who passed away 46 years old in recently.
It was the first major televised fight night in the city since the passing of Hatton. As the last bell faded, the silence gave way to a chant of "there's just one Ricky Hatton".
The action within the ring reflected the sentiment. Arthur was knocked down by a left hook flush on the chin in the early round, standing uncertainly to his footing on the count of eight.
But the red-colored shorts of the fighter soon pressed ahead again. Across the ring, Rea - in competitive blue - was injured early, noticeable damage appearing under his orbital area as the fighters landed punishing blows.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, responded in kind with effective uppercuts as the intensity hardly diminished over the full distance.
The victor edged the decision with official scores of even score, close margin and 115-112, but each competitor were persistent and brave, exactly what their inspiration the legend represented.
