British light heavyweight Buatsi made a winning yet unimpressive debut to life under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a split decision in a close 10-round bout at the Manchester venue.
But Parker landed significant shots, landing some telling individual punches in a fight where the techniques never quite clicked, with constant grabbing marring the contest.
Two judges had it 96-94 in favor to Buatsi, with the final judge a even score.
"It wasn't my finest performance but how do champions respond? They succeed," Buatsi said in the ring as he was greeted with disapproval from the crowd.
The British fighter bounced back after his maiden career setback - an epic battle with his previous opponent in February - to earn a 20th career victory.
Several boxing experts felt the challenger, 31, merited the decision but the Derbyshire fighter experienced the second setback of his 28-bout career.
Buatsi Earns Victory in Slow Affair
His career development has slowed in recent times through contract problems and long spells of lack of fights.
Earlier forecast as the future of the British fight scene, he now stands trying to fulfil that early promise - possibly in what feels like a final roll of the dice - under recent support.
He began cautiously, with neither fighter prepared to be aggressive in a cagey opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in two years ago after breaking his hand mid-fight, was participating in his second bout at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for the favorite, who worked behind a solid defense to narrowly win the better stanzas.
The audience's tolerance decreased amid regular grabbing, with the challenger going down several times during clinches.
The underdog ended stronger, but multiple periods were difficult to score. Nevertheless, former world champion Carl Frampton - working with the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just only one stanza.
Buatsi advances, but with the presence of heavy hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still looks steep.
Hatton Homage Motivates Local Rivalry Contest
In the supporting bout, Arthur overcame Rea by divided decision in a excellent local rivalry contest to capture the European light-heavyweight championship.
The venue fell silent for a extremely emotional memorial before the fight as a bell ceremony sounded in remembrance of Manchester's own Hatton, who died 46 years old in recently.
It was the premier televised boxing event in the location since Hatton's death. As the concluding sound faded, the stillness became a roar of "there's only one Hatton".
The fighting inside the ropes equaled the sentiment. Arthur was knocked down by a significant blow directly to the chin in the initial stage, rising shakily to his position on the eight count.
But the red-colored equipment of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was marked up early, heavy swelling developing under his eye as the duo landed hard punches.
Rea, 27, connected with strong blows but Arthur, thirty-four, fought fire with fire with effective uppercuts as the action hardly diminished over twelve rounds.
Arthur barely secured the result with judges scorecards of even score, close margin and clearer margin, but both fighters were determined and courageous, everything their hero the legend stood for.
