UK light-heavyweight Buatsi earned a win yet disappointing start to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a split decision in a tight ten-round bout at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful individual punches in a match where the techniques never quite clicked, with frequent clinching marring the contest.
Two judges had it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my best showing but how do champions respond? They succeed," the victor commented 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 memorable fight with his previous opponent in February - to secure a 20th pro success.
Several boxing experts thought the challenger, thirty-one, deserved the win but the contender suffered the second defeat of his 28-fight professional journey.
The Champion Earns Triumph in Uneventful Match
His career development has plateaued in recent times through promotional disputes and considerable time of lack of fights.
Previously predicted as the rising talent of UK boxing, he now finds himself trying to fulfil that early promise - perhaps in what seems like a ultimate opportunity - under recent support.
He started carefully, with the two boxers willing to take risks in a cagey early stages.
Parker, whose only previous defeat came at the lower weight class against John Ryder in 2022 after damaging his hand during the bout, was competing in only his second bout at light heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for Buatsi, who utilized a solid defense to narrowly win the better rounds.
The audience's tolerance diminished because of constant clinching, with the challenger going down multiple occasions during close exchanges.
The underdog closed well, but multiple periods were hard to judge. Although, previous titleholder the boxing analyst - commentating on Dazn - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
The victor advances, but with the caliber of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still appears challenging.
Hatton Memorial Motivates Local Rivalry Fight
In the co-main event, Arthur overcame Rea by split-decision in a excellent Manchester vs Manchester battle to capture the continental title.
The stadium became quiet for a profoundly moving tribute before the fight as ten bells sounded in memory of Manchester's own Hatton, who died 46 years old in last month.
It was the premier televised match card in the location since Hatton's passing. As the concluding sound faded, the stillness transitioned to a chant of "only one Hatton".
The fighting during the bout reflected the emotion. The eventual winner was floored by a powerful punch directly to the jaw in the early round, getting up unsteadily to his footing on the eight count.
But the red-colored equipment of Arthur soon came forward again. On the opposite side, the opponent - in competitive blue - was damaged quickly, significant bruising forming under his orbital area as the pair traded powerful shots.
The challenger, 27, connected with strong blows but Arthur, 34, matched the intensity with effective uppercuts as the pace hardly diminished over the full distance.
Arthur narrowly won the result with scoring tallies of 114-114, narrow lead and 115-112, but each competitor were relentless and courageous, everything their inspiration the legend stood for.
