British light heavyweight Buatsi made a winning yet disappointing debut to life under new promoters with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a split decision in a tight 10-round bout at the boxing arena.
But Parker had his moments, landing some telling single shots in a fight where the techniques failed to mesh, with constant grabbing spoiling the contest.
Two judges had it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my finest performance but how do champions respond? They succeed," Buatsi said in the ringside as he was met by disapproval from the audience.
The British fighter bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to secure a 20th pro success.
Various analysts felt Parker, thirty-one, deserved the decision but the British boxer suffered the second loss of his 28-match career.
Buatsi Claims Victory in Slow Encounter
Buatsi's progress has plateaued in recent times through promotional disputes and extended periods of inactivity.
Once tipped as the future of British boxing, he now stands trying to realize his potential - perhaps in what appears to be a final roll of the dice - under recent support.
He opened tentatively, with neither fighter willing to take risks in a tentative initial rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after damaging his hand mid-fight, was competing in only his second bout at light heavyweight.
By the middle rounds, the underdog had kept it close, creating difficulties for the favorite, who worked behind a tight guard to narrowly win the more effective stanzas.
The audience's tolerance decreased during regular grabbing, with the challenger slipping to the canvas several times during grappling.
The underdog closed well, but several stanzas were challenging to assess. However, former world champion the boxing analyst - working with the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just a single round.
The victor advances, but with the likes of power puncher David Benavidez, and Russian champion Bivol ruling the division, the path to championship success - based on this performance - still seems difficult.
Hatton Memorial Motivates Local Rivalry Battle
In the secondary fight, Arthur overcame Rea by divided decision in a excellent local rivalry battle to secure the European light heavyweight championship.
The arena grew hushed for a deeply poignant tribute before the fight as ten bells tolled in remembrance of Manchester's own Hatton, who succumbed 46 years old in last month.
It was the premier televised boxing event in the urban center since the passing of Hatton. As the last bell faded, the silence transitioned to a shout of "there's just one Ricky Hatton".
The action within the ring reflected the feeling. The eventual winner was floored by a significant blow directly to the face in the early round, rising shakily to his position on the referee's count.
But the traditional red shorts of Arthur soon advanced again. On the opposite side, Rea - in competitive blue - was marked up early, significant bruising developing under his face as the duo exchanged punishing blows.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, responded in kind with stinging uppercuts as the action seldom decreased over 12 rounds.
The victor narrowly won the result with scoring tallies of even score, narrow lead and 115-112, but both fighters were persistent and brave, all the qualities their inspiration the legend embodied.
