British light-heavyweight Buatsi earned a win yet unimpressive start to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a split decision in a close 10-round fight at the Manchester venue.
But the challenger landed significant shots, connecting with powerful single shots in a fight where the techniques failed to mesh, with constant grabbing disrupting the action.
The scoring judges scored it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest performance but what defines champions? They prevail," the victor stated in the ring as he was met by disapproval from the audience.
The Londoner got back to winning after his maiden career setback - an thrilling contest with Callum Smith in last winter - to earn a twentieth professional win.
Several boxing experts believed the challenger, 31, deserved the victory but the contender endured the second loss of his 28-match professional journey.
The Champion Earns Triumph in Uneventful Match
The fighter's advancement has stalled in recent times through management issues and long spells of inactivity.
Earlier forecast as the next star of British boxing, he now is positioned trying to realize his potential - maybe in what seems like a final roll of the dice - under fresh management.
He began cautiously, with the two boxers willing to overcommit in a calculated early stages.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in two years ago after breaking his hand mid-fight, was making just his second bout at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, causing problems for the favorite, who worked behind a solid defense to edge the better periods.
The audience's tolerance wore thin during regular grabbing, with the challenger slipping to the canvas multiple occasions during close exchanges.
The underdog ended stronger, but multiple periods were hard to judge. Although, former world champion Carl Frampton - commentating on Dazn - had it strongly leaning for the challenger, giving Buatsi just only one stanza.
Buatsi progresses, but with the presence of hard hitter David Benavidez, and Eastern European fighter Bivol leading the category, the path to championship success - on this evidence - still seems difficult.
Hatton Homage Fuels Local Rivalry Contest
In the supporting bout, Lyndon Arthur overcame Rea by divided decision in a terrific Manchester vs Manchester battle to win the continental championship.
The venue grew hushed for a extremely emotional memorial prior to the bout as a bell ceremony sounded in memory of Manchester's own Hatton, who succumbed at age 46 in September.
It was the first major televised boxing event in the city since the passing of Hatton. As the last bell faded, the silence transitioned to a chant of "there's just one Ricky Hatton".
The fighting within the ring reflected the feeling. The eventual winner was floored by a powerful punch squarely on the jaw in the early round, getting up unsteadily to his position on the referee's count.
But the red-colored equipment of the fighter soon came forward again. From the other corner, the opponent - in opposing blue - was marked up quickly, noticeable damage forming under his orbital area as the duo traded punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, matched the intensity with powerful upward punches as the action seldom decreased over 12 rounds.
Arthur edged the verdict with judges scorecards of even score, narrow lead and wider gap, but the two athletes were persistent and full of heart, exactly what their idol the legend represented.
