UK light-heavyweight Buatsi secured a victory yet unimpressive debut to life under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a split decision in a tight 10-round fight at the boxing arena.
But Parker found success, connecting with powerful individual punches in a fight where the approaches didn't complement each other, with constant grabbing spoiling the contest.
The scoring judges judged it 96-94 to the winner, with the final judge a 95-95.
"It wasn't my finest performance but how do champions respond? They succeed," Buatsi said in the arena as he was faced negative reactions from the audience.
The Londoner bounced back after his maiden career setback - an thrilling contest with Callum Smith in last winter - to earn a 20th career victory.
Several boxing experts believed the challenger, 31, should have been awarded the victory but the contender endured the second setback of his 28-fight professional journey.
Buatsi Earns Victory in Dull Affair
The fighter's advancement has stalled in recent times through management issues and considerable time of inactivity.
Previously predicted as the future of UK boxing, he now finds himself trying to fulfil that early promise - possibly in what feels like a last chance - under new promotional backing.
He opened tentatively, with neither fighter prepared to take risks in a cagey initial rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand during the bout, was making just his second appearance at light heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who worked behind a tight guard to edge the more effective periods.
The audience's tolerance decreased because of 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. However, ex-champion Carl Frampton - working with the broadcast network - had it significantly in favor for Parker, awarding Buatsi just a single round.
Buatsi progresses, but with the likes of power puncher Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Tribute Fuels Manchester Derby Battle
In the co-main event, Arthur defeated Rea by close verdict in a outstanding all-Manchester battle to win the continental belt.
The venue grew hushed for a extremely emotional tribute ahead of the contest as ten bells sounded in remembrance of local hero Hatton, who died 46 years old in September.
It was the initial significant broadcast match card in the urban center since the passing of Hatton. As the final chime ended, the silence became a shout of "there's just one Hatton".
The competition inside the ropes matched the feeling. Arthur was floored by a powerful punch squarely on the jaw in the initial stage, getting up unsteadily to his position on the eight count.
But the Manchester United-red shorts of Arthur soon pressed ahead again. From the other corner, the opponent - in competitive blue - was damaged soon, noticeable damage appearing under his eye as the pair landed punishing blows.
Rea, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with powerful upward punches as the action hardly diminished over the full distance.
The victor barely secured the decision with official scores of even score, close margin and clearer margin, but each competitor were relentless and courageous, all the qualities their inspiration the legend represented.
