British light heavyweight Buatsi made a winning yet disappointing beginning to his career under recent management with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a majority decision in a tight 10-round bout at the Co-op Live Arena.
But the challenger found success, connecting with powerful clean blows in a match where the styles failed to mesh, with frequent clinching marring the action.
Two judges had it 96-94 in favor to Buatsi, with the final judge a 95-95.
"It wasn't my best performance but what defines champions? They prevail," the victor stated in the ringside as he was met by disapproval from the spectators.
The Londoner bounced back after his maiden career setback - an thrilling contest with Callum Smith in last winter - to secure a 20th pro success.
Several boxing experts thought the challenger, 31, should have been awarded the victory but the contender experienced the second setback of his 28-match career.
The Champion Claims Win in Slow Encounter
Buatsi's progress has slowed in recent years through contract problems and considerable time of inactivity.
Once tipped as the future of UK boxing, he now finds himself 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 be aggressive in a cagey early stages.
The challenger, whose single earlier setback came at super middleweight against his former opponent in 2022 after damaging his hand during the bout, was making just his second appearance at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, making life awkward for the favorite, who worked behind a tight guard to narrowly win the better rounds.
The spectators' acceptance decreased amid regular grabbing, with the challenger falling to the floor several times during grappling.
The underdog closed well, but multiple periods were difficult to score. However, ex-champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, giving Buatsi just one round.
Buatsi progresses, but with the caliber of power puncher Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Memorial Inspires All-Manchester Battle
In the secondary fight, Arthur overcame Rea by split-decision in a outstanding all-Manchester contest to secure the European light heavyweight title.
The arena grew hushed for a deeply poignant tribute prior to the bout as ten bells sounded in remembrance of local hero Ricky Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast match card in the city since the passing of Hatton. As the concluding sound faded, the silence became a shout of "there's only one Ricky Hatton".
The competition during the bout equaled the feeling. Arthur was floored by a powerful punch directly to the chin in the initial stage, standing uncertainly to his position on the eight count.
But the traditional red attire of the fighter soon came forward again. Across the ring, the opponent - in competitive blue - was damaged soon, noticeable damage forming under his eye as the duo landed powerful shots.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the intensity seldom decreased over 12 rounds.
Arthur barely secured the verdict with judges scorecards of even score, close margin and 115-112, but both fighters were determined and courageous, everything their inspiration Hatton embodied.
