British light-heavyweight Buatsi made a winning yet underwhelming beginning to his career under new promoters with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's punch output appeared to earn him a split decision in a close ten-round fight at the boxing arena.
But the challenger landed significant shots, connecting with powerful clean blows in a contest where the approaches never quite clicked, with excessive holding disrupting the contest.
Two judges had it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my best performance but what do champions do? They succeed," Buatsi stated in the arena as he was faced disapproval from the audience.
The Londoner got back to winning after his first professional defeat - an thrilling contest with his previous opponent in February - to secure a twentieth professional win.
Some ringside observers felt Parker, thirty-one, deserved the decision but the Derbyshire fighter experienced the second defeat of his 28-fight professional journey.
Buatsi Claims Victory in Dull Match
His career development has plateaued in recent years through management issues and extended periods of inactivity.
Earlier forecast as the future of the British fight scene, he now is positioned trying to achieve expectations - perhaps in what appears to be a final roll of the dice - under new promotional backing.
He opened tentatively, with both competitors prepared to overcommit in a calculated opening few rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in two years ago after damaging his hand mid-fight, was making just his second bout at light-heavyweight.
By the middle rounds, Parker had stayed in contention, causing problems for the favorite, who worked behind a protective stance to edge the more effective rounds.
The audience's tolerance wore thin amid constant clinching, with Parker slipping to the canvas multiple occasions during clinches.
The underdog finished the stronger, but several stanzas were difficult to score. However, former world champion Carl Frampton - commentating on the broadcast network - had it significantly in favor for Parker, awarding Buatsi just a single round.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Tribute Fuels Manchester Derby Battle
In the co-main event, Arthur beat Bradley Rea by divided decision in a outstanding local rivalry contest to capture the European light heavyweight championship.
The arena grew hushed for a profoundly moving tribute ahead of the contest as a bell ceremony sounded in remembrance of the city's native Hatton, who passed away at age 46 in recently.
It was the first major televised match card in the city since Hatton's death. As the last bell faded, the stillness transitioned to a chant of "there's only one Ricky Hatton".
The action during the bout reflected the feeling. The eventual winner was knocked down by a left hook squarely on the chin in the second round, rising shakily to his position on the count of eight.
But the Manchester United-red attire of the fighter soon came forward again. From the other corner, the opponent - in rival City blue - was damaged early, noticeable damage developing under his face as the pair exchanged hard punches.
The challenger, 27, landed power punches but the champion, 34, fought fire with fire with stinging uppercuts as the intensity hardly diminished over 12 rounds.
Arthur narrowly won the result with scoring tallies of even score, narrow lead and 115-112, but the two athletes were persistent and courageous, exactly what their hero the legend represented.
