British light-heavyweight Buatsi made a winning yet disappointing start to his career under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a judges' verdict in a competitive 10-round fight at the boxing arena.
But Parker landed significant shots, connecting with powerful single shots in a match where the techniques didn't complement each other, with frequent clinching spoiling the contest.
Two judges scored it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my finest display but what defines champions? They win," the victor commented in the ring as he was greeted with boos from the spectators.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in February - to claim a 20th career victory.
Various analysts believed the challenger, 31, should have been awarded the decision but the contender suffered the second defeat of his 28-match career.
The Champion Secures Victory in Uneventful Match
Buatsi's progress has plateaued in the past few years through contract problems and long spells of lack of fights.
Earlier forecast as the rising talent of UK boxing, he now finds himself trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter willing to overcommit in a cagey early stages.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after suffering a hand injury in the contest, was competing in only his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, creating difficulties for the favorite, who utilized a protective stance to edge the more effective stanzas.
The crowd's patience decreased amid constant clinching, with Parker falling to the floor various instances during close exchanges.
The underdog ended stronger, but many rounds were difficult to score. Nevertheless, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi progresses, but with the presence of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Hatton Homage Motivates All-Manchester Fight
In the secondary fight, Lyndon Arthur defeated Bradley Rea by close verdict in a terrific all-Manchester fight to secure the European light-heavyweight title.
The arena fell silent for a profoundly moving tribute before the fight as 10 bells sounded in memory of Manchester's own Hatton, who succumbed 46 years old in September.
It was the premier televised boxing event in the urban center since Hatton's death. As the last bell ended, the quiet transitioned to a roar of "only one Hatton".
The fighting within the ring equaled the feeling. The eventual winner was floored by a left hook flush on the jaw in the early round, standing uncertainly to his position on the count of eight.
But the red-colored shorts of Arthur soon came forward again. On the opposite side, the opponent - in rival City blue - was marked up early, heavy swelling appearing under his orbital area as the pair exchanged powerful shots.
The challenger, 27, delivered effective strikes but the champion, thirty-four, matched the intensity with powerful upward punches as the intensity hardly diminished over twelve rounds.
The victor edged the verdict with official scores of 114-114, 115-113 and 115-112, but each competitor were persistent and courageous, everything their inspiration the legend embodied.
