British light heavyweight Buatsi secured a victory yet underwhelming debut to life under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a competitive 10-round contest at the boxing arena.
But the challenger had his moments, landing some telling clean blows in a fight where the techniques didn't complement each other, with frequent clinching disrupting the contest.
The scoring judges scored it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest performance but how do champions respond? They prevail," the victor stated in the ringside as he was met by disapproval from the spectators.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in February - to earn a 20th pro success.
Various analysts believed the challenger, thirty-one, merited the victory but the British boxer suffered the second setback of his 28-fight career.
Buatsi Earns Win in Uneventful Match
Buatsi's progress has slowed in recent times through promotional disputes and extended periods of lack of fights.
Previously predicted as the rising talent of UK boxing, he now finds himself trying to realize his potential - possibly in what feels like a final roll of the dice - under fresh management.
He began cautiously, with the two boxers prepared to overcommit in a tentative initial rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after damaging his hand mid-fight, was making just his second appearance at the higher weight class.
By the middle rounds, Parker had stayed in contention, causing problems for Buatsi, who worked behind a protective stance to barely take the better rounds.
The spectators' acceptance decreased during constant clinching, with the challenger falling to the floor multiple occasions during clinches.
The underdog finished the stronger, but many rounds were difficult to score. Although, former world champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, giving Buatsi just one round.
Buatsi moves on, but with the likes of heavy hitter Benavidez, and Russian star Bivol dominating the weight class, the journey to titles - on this evidence - still seems difficult.
Hatton Tribute Fuels Manchester Derby Contest
In the supporting bout, Arthur defeated Rea by close verdict in a excellent all-Manchester contest to secure the continental title.
The venue became quiet for a deeply poignant memorial prior to the bout as a bell ceremony rang in memory of Manchester's own Ricky Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast match card in the location since Hatton's passing. As the final chime disappeared, the silence gave way to a shout of "there's only one Hatton".
The competition inside the ropes reflected the emotion. The eventual winner was sent to the canvas by a powerful punch squarely on the jaw in the early round, rising shakily to his position on the referee's count.
But the red-colored attire of Arthur soon came forward again. From the other corner, the opponent - in opposing blue - was damaged soon, heavy swelling appearing under his orbital area as the pair traded powerful shots.
Rea, 27, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the pace seldom decreased over twelve rounds.
Arthur edged the result with official scores of draw, 115-113 and clearer margin, but each competitor were persistent and brave, exactly what their idol Hatton embodied.
