British light heavyweight Buatsi made a winning yet disappointing beginning to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a majority decision in a tight ten-round bout at the boxing arena.
But Parker found success, landing some telling clean blows in a contest where the styles failed to mesh, with constant grabbing disrupting the contest.
The officials had it 96-94 for to Buatsi, with the third a even score.
"It wasn't my best showing but how do champions respond? They succeed," the victor commented in the ring as he was met by negative reactions from the audience.
The British fighter bounced back after his first professional defeat - an epic battle with his previous opponent in February - to earn a 20th pro success.
Several boxing experts thought Parker, thirty-one, should have been awarded the victory but the British boxer experienced the second loss of his 28-match career.
The Champion Earns Win in Dull Affair
The fighter's advancement has plateaued in recent years through management issues and considerable time of lack of fights.
Once tipped as the future of the British fight scene, he now finds himself trying to fulfil that early promise - maybe in what appears to be a last chance - under recent support.
He opened tentatively, with both competitors ready to overcommit in a tentative initial rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after breaking his hand during the bout, was making just his second bout at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for Buatsi, who worked behind a solid defense to edge the better rounds.
The crowd's patience diminished because of regular grabbing, with Parker falling to the floor several times during grappling.
The underdog finished the stronger, but multiple periods were challenging to assess. However, previous titleholder Carl Frampton - working with Dazn - had it significantly in favor for Parker, awarding Buatsi just only one stanza.
Buatsi moves on, but with the likes of hard hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the road to world glory - based on this performance - still appears challenging.
Hatton Memorial Inspires Manchester Derby Battle
In the secondary fight, Arthur defeated Bradley Rea by split-decision in a excellent all-Manchester battle to secure the continental title.
The venue fell silent for a profoundly moving tribute prior to the bout as ten bells rang in honor of local hero Ricky Hatton, who passed away 46 years old in September.
It was the initial significant broadcast fight night in the location since Hatton's passing. As the concluding sound faded, the quiet transitioned to a shout of "there's only one Ricky Hatton".
The fighting during the bout matched the feeling. Arthur was sent to the canvas by a left hook squarely on the face in the second round, rising shakily to his footing on the eight count.
But the traditional red shorts of the fighter soon advanced again. On the opposite side, Rea - in competitive blue - was marked up early, significant bruising forming under his orbital area as the duo landed hard punches.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, matched the intensity with powerful upward punches as the pace rarely dropped over 12 rounds.
The victor barely secured the verdict with judges scorecards of draw, narrow lead and wider gap, but both fighters were persistent and courageous, everything their hero Hatton stood for.
