UK light heavyweight Buatsi made a winning yet underwhelming debut to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output appeared to earn him a judges' verdict in a tight ten-round contest at the Manchester venue.
But Parker landed significant shots, connecting with powerful individual punches in a fight where the techniques didn't complement each other, with excessive holding marring the action.
The officials scored it 96-94 in favor to the winner, with the third a even score.
"It wasn't my best showing but what defines champions? They prevail," Buatsi commented in the ringside as he was met by disapproval from the spectators.
The British fighter bounced back after his initial pro loss - an thrilling contest with his previous opponent in last winter - to secure a twentieth professional win.
Several boxing experts believed Parker, 31, deserved the win but the contender endured the second setback of his 28-bout professional journey.
Buatsi Secures Win in Dull Match
Buatsi's progress has plateaued in the past few years through management issues and long spells of inactivity.
Previously predicted as the next star of British boxing, he now is positioned trying to realize his potential - maybe in what appears to be a ultimate opportunity - under recent support.
He began cautiously, with the two boxers ready to take risks in a tentative early stages.
Parker, whose only previous defeat came at the lower weight class against his former opponent in two years ago after damaging his hand mid-fight, was making just his second fight at light heavyweight.
By the middle rounds, Parker had made it competitive, making life awkward for Buatsi, who worked behind a protective stance to edge the cleaner rounds.
The spectators' acceptance decreased during constant clinching, with Parker slipping to the canvas various instances during grappling.
The underdog ended stronger, but several stanzas were hard to judge. Although, former world champion the boxing analyst - working with Dazn - had it significantly in favor for Parker, scoring for Buatsi just one round.
Buatsi progresses, but with the likes of power puncher Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - judging by this showing - still seems difficult.
Hatton Memorial Inspires Local Rivalry Contest
In the supporting bout, Arthur defeated Bradley Rea by divided decision in a excellent local rivalry fight to win the continental belt.
The venue became quiet for a profoundly moving tribute before the fight as ten bells sounded in memory of the city's native Ricky Hatton, who died aged 46 in September.
It was the premier televised match card in the location since Hatton's passing. As the final chime disappeared, the silence gave way to a shout of "there's only one Ricky Hatton".
The fighting during the bout equaled the emotion. The eventual winner was knocked down by a powerful punch squarely on the jaw in the initial stage, rising shakily to his footing on the referee's count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. Across the ring, Rea - in rival City blue - was injured quickly, significant bruising forming under his orbital area as the pair traded hard punches.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, matched the intensity with powerful upward punches as the action seldom decreased over the full distance.
Arthur narrowly won the result with judges scorecards of even score, narrow lead and clearer margin, but the two athletes were persistent and courageous, everything their inspiration Hatton stood for.
