UK light-heavyweight Buatsi earned a win yet underwhelming debut to life under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a tight 10-round fight at the Manchester venue.
But Parker had his moments, landing some telling single shots in a contest where the approaches failed to mesh, with constant grabbing spoiling the fight.
The scoring judges had it 96-94 for to Buatsi, with the third a even score.
"It wasn't my greatest performance but what defines champions? They win," the victor commented in the arena as he was faced boos from the audience.
The Londoner got back to winning after his initial pro loss - an epic battle with his previous opponent in February - to earn a 20th career victory.
Several boxing experts thought Parker, 31, should have been awarded the win but the Derbyshire fighter suffered the second setback of his 28-match career.
Buatsi Secures Triumph in Dull Match
The fighter's advancement has slowed in recent years through management issues and considerable time of inactivity.
Earlier forecast as the future of the British fight scene, he now is positioned trying to fulfil that early promise - maybe in what feels like a ultimate opportunity - under recent support.
He started carefully, with neither fighter prepared to overcommit in a calculated early stages.
Parker, whose only previous defeat came at super middleweight against his former opponent in 2022 after breaking his hand during the bout, was participating in his second bout at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, creating difficulties for Buatsi, who utilized a protective stance to narrowly win the more effective stanzas.
The spectators' acceptance diminished because of constant clinching, with Parker going down several times during grappling.
Parker finished the stronger, but several stanzas were challenging to assess. Nevertheless, previous titleholder the boxing analyst - working with Dazn - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
The victor advances, but with the likes of heavy hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - on this evidence - still appears challenging.
Hatton Tribute Inspires Local Rivalry Fight
In the co-main event, Arthur beat Rea by divided decision in a outstanding Manchester vs Manchester contest to secure the European light heavyweight championship.
The arena became quiet for a profoundly moving tribute prior to the bout as ten bells tolled in remembrance of local hero Ricky Hatton, who succumbed 46 years old in last month.
It was the first major televised fight night in the urban center since Hatton's death. As the last bell faded, the stillness gave way to a chant of "there's just one Ricky Hatton".
The action within the ring matched the feeling. The eventual winner was sent to the canvas by a left hook directly to the chin in the initial stage, rising shakily to his footing on the eight count.
But the Manchester United-red attire of the fighter soon pressed ahead again. Across the ring, Rea - in opposing blue - was injured early, noticeable damage appearing under his orbital area as the fighters exchanged hard punches.
The challenger, 27, landed power punches but the champion, thirty-four, matched the intensity with stinging uppercuts as the action seldom decreased over 12 rounds.
Arthur narrowly won the decision with judges scorecards of even score, narrow lead and 115-112, but both fighters were determined and courageous, all the qualities their idol Hatton embodied.
