British light heavyweight Buatsi made a winning yet unimpressive debut to life under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a majority decision in a tight ten-round contest at the Manchester venue.
But Parker found success, landing some telling clean blows in a contest where the approaches never quite clicked, with excessive holding marring the fight.
Two judges scored it 96-94 to the winner, with the third a 95-95.
"It wasn't my finest showing but how do champions respond? They prevail," Buatsi commented in the ring as he was faced boos from the audience.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in last winter - to claim a 20th career victory.
Various analysts thought the challenger, 31, should have been awarded the victory but the contender suffered the second loss of his 28-bout professional journey.
The Champion Claims Win in Slow Encounter
His career development has slowed in recent years through management issues and considerable time of lack of fights.
Earlier forecast as the next star of the British fight scene, 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 both competitors willing to overcommit in a calculated initial rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in 2022 after breaking his hand mid-fight, was competing in only his second appearance at light-heavyweight.
By the middle rounds, Parker had made it competitive, making life awkward for the favorite, who operated with a solid defense to barely take the cleaner rounds.
The spectators' acceptance decreased amid constant clinching, with Parker falling to the floor various instances during clinches.
Parker ended stronger, but several stanzas were hard to judge. Nevertheless, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, giving Buatsi just one round.
The victor progresses, but with the caliber of heavy hitter David Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - based on this performance - still looks steep.
Hatton Tribute Motivates All-Manchester Contest
In the supporting bout, Lyndon Arthur beat Rea by divided decision in a excellent local rivalry fight to secure the European light-heavyweight championship.
The stadium fell silent for a extremely emotional homage prior to the bout as a bell ceremony sounded in remembrance of the city's native Hatton, who passed away 46 years old in September.
It was the initial significant broadcast match card in the location since the passing of Hatton. As the final chime ended, the quiet transitioned to a roar of "there's only one Hatton".
The competition during the bout reflected the feeling. The eventual winner was sent to the canvas by a left hook squarely on the chin in the early round, rising shakily to his position on the eight count.
But the traditional red shorts of the fighter soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was marked up soon, heavy swelling forming under his orbital area as the fighters exchanged punishing blows.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with effective uppercuts as the pace hardly diminished over twelve rounds.
The victor narrowly won the result with judges scorecards of draw, narrow lead and clearer margin, but both fighters were relentless and full of heart, all the qualities their hero Hatton embodied.
