British light heavyweight Buatsi made a winning yet underwhelming beginning to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a split decision in a close ten-round contest at the Manchester venue.
But the challenger found success, connecting with powerful single shots in a match where the techniques failed to mesh, with constant grabbing marring the fight.
The scoring judges judged it 96-94 to Buatsi, with the third a even score.
"It wasn't my finest showing but what defines champions? They succeed," Buatsi stated in the arena as he was greeted with disapproval from the crowd.
The Londoner got back to winning after his maiden career setback - an memorable fight with his previous opponent in February - to claim a 20th pro success.
Various analysts felt the challenger, thirty-one, merited the victory but the contender experienced the second defeat of his 28-fight career.
Buatsi Claims Win in Dull Match
Buatsi's progress has slowed in recent years through management issues and considerable time of lack of fights.
Earlier forecast as the next star of the British fight scene, he now stands trying to achieve expectations - perhaps in what seems like a final roll of the dice - under fresh management.
He began cautiously, with both competitors willing to overcommit in a calculated opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second appearance at light-heavyweight.
By the halfway stage, Parker had stayed in contention, creating difficulties for Buatsi, who worked behind a protective stance to edge the cleaner periods.
The spectators' acceptance decreased amid constant clinching, with the challenger falling to the floor various instances during close exchanges.
The underdog ended stronger, but many rounds were hard to judge. Nevertheless, former world champion the boxing analyst - commentating on Dazn - had it significantly in favor for the challenger, giving Buatsi just one round.
Buatsi advances, but with the presence of power puncher David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still seems difficult.
Hatton Memorial Fuels Manchester Derby Battle
In the supporting bout, Arthur beat Bradley Rea by split-decision in a excellent all-Manchester battle to capture the European light-heavyweight title.
The venue became quiet for a deeply poignant tribute ahead of the contest as ten bells rang in memory of the city's native Hatton, who succumbed at age 46 in recently.
It was the first major televised fight night in the city since the passing of Hatton. As the final chime faded, the silence became a shout of "there's just one Ricky Hatton".
The action within the ring reflected the sentiment. The eventual winner was knocked down by a powerful punch flush on the jaw in the initial stage, getting up unsteadily to his position on the referee's count.
But the Manchester United-red shorts of the fighter soon came forward again. Across the ring, the opponent - in rival City blue - was damaged early, significant bruising developing under his orbital area as the duo traded powerful shots.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the action seldom decreased over 12 rounds.
The victor edged the verdict with scoring tallies of even score, close margin and 115-112, but the two athletes were determined and brave, all the qualities their inspiration the legend represented.
