British light heavyweight Buatsi made a winning yet disappointing beginning to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a majority decision in a close 10-round contest at the boxing arena.
But the challenger landed significant shots, connecting with powerful individual punches in a contest where the approaches didn't complement each other, with excessive holding marring the contest.
The scoring judges scored it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest showing but what do champions do? They win," the victor stated in the ring as he was faced negative reactions from the audience.
The British fighter bounced back after his maiden career setback - an epic battle with Callum Smith in February - to secure a 20th pro success.
Some ringside observers believed the challenger, 31, merited the decision but the British boxer endured the second defeat of his 28-bout career.
Buatsi Earns Win in Uneventful Encounter
His career development has stalled in the past few years through management issues and considerable time of inactivity.
Earlier forecast as the next star of British boxing, he now stands trying to realize his potential - possibly in what feels like a final roll of the dice - under new promotional backing.
He opened tentatively, with both competitors prepared to take risks in a calculated early stages.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after damaging his hand mid-fight, was participating in his second fight at light heavyweight.
By the fight's midpoint, Parker had kept it close, causing problems for the favorite, who operated with a solid defense to narrowly win the more effective stanzas.
The spectators' acceptance wore thin amid constant clinching, with Parker falling to the floor several times during close exchanges.
Parker closed well, but several stanzas were challenging to assess. Nevertheless, previous titleholder the boxing analyst - working with Dazn - had it significantly in favor for the challenger, scoring for Buatsi just a single round.
Buatsi moves on, but with the caliber of power puncher David Benavidez, and Eastern European fighter Bivol leading the category, the journey to titles - based on this performance - still appears challenging.
Ricky Hatton Tribute Inspires Local Rivalry Fight
In the secondary fight, Arthur defeated Bradley Rea by divided decision in a excellent Manchester vs Manchester fight to capture the European light-heavyweight championship.
The stadium grew hushed for a deeply poignant memorial prior to the bout as 10 bells rang in remembrance of local hero Ricky Hatton, who passed away at age 46 in last month.
It was the first major televised match card in the urban center since the passing of Hatton. As the final chime faded, the quiet gave way to a shout of "there's only one Hatton".
The fighting during the bout equaled the feeling. The eventual winner was floored by a significant blow flush on the face in the second round, getting up unsteadily to his position on the eight count.
But the traditional red equipment of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was damaged early, significant bruising developing under his face as the pair traded powerful shots.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with powerful upward punches as the action hardly diminished over 12 rounds.
Arthur barely secured the result with scoring tallies of draw, close margin and 115-112, but each competitor were persistent and full of heart, exactly what their inspiration the legend stood for.
