UK light-heavyweight Buatsi made a winning yet unimpressive debut to his career under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a judges' verdict in a close ten-round fight at the boxing arena.
But Parker landed significant shots, landing some telling individual punches in a contest where the styles failed to mesh, with excessive holding spoiling the action.
The officials had it 96-94 to Buatsi, with the third a even score.
"It wasn't my best performance but how do champions respond? They prevail," Buatsi said in the arena as he was met by disapproval from the spectators.
The British fighter returned to winning ways after his maiden career setback - an epic battle with his previous opponent in last winter - to earn a 20th career victory.
Some ringside observers believed Parker, 31, merited the victory but the British boxer endured the second loss of his 28-bout career.
The Champion Claims Victory in Slow Affair
His career development has plateaued in recent times through contract problems and extended periods of lack of fights.
Previously predicted as the future of UK boxing, he now finds himself trying to fulfil that early promise - possibly in what appears to be a last chance - under new promotional backing.
He started carefully, with both competitors ready to overcommit in a calculated opening few rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after damaging his hand during the bout, was participating in his second appearance at light heavyweight.
By the middle rounds, the underdog had stayed in contention, creating difficulties for Buatsi, who utilized a solid defense to edge the cleaner stanzas.
The spectators' acceptance decreased because of constant clinching, with the challenger going down various instances during close exchanges.
Parker finished the stronger, but many rounds were difficult to score. However, ex-champion the boxing analyst - working with the broadcast network - had it particularly wide for Parker, giving Buatsi just only one stanza.
Buatsi advances, but with the presence of hard hitter David Benavidez, and Russian star Bivol ruling the division, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Tribute Motivates Local Rivalry Fight
In the supporting bout, Lyndon Arthur overcame Bradley Rea by close verdict in a outstanding all-Manchester contest to capture the European light heavyweight belt.
The stadium became quiet for a extremely emotional homage before the fight as ten bells tolled in memory of Manchester's own Hatton, who passed away at age 46 in September.
It was the premier televised fight night in the city since Hatton's passing. As the concluding sound disappeared, the stillness transitioned to a roar of "there's just one Hatton".
The fighting during the bout equaled the sentiment. Arthur was sent to the canvas by a powerful punch squarely on the face in the early round, rising shakily to his feet on the count of eight.
But the Manchester United-red equipment of Arthur soon advanced again. On the opposite side, Rea - in rival City blue - was injured soon, noticeable damage forming under his face as the duo exchanged punishing blows.
Rea, 27, delivered effective strikes but Arthur, 34, fought fire with fire with effective uppercuts as the intensity seldom decreased over 12 rounds.
Arthur barely secured the verdict with judges scorecards of 114-114, 115-113 and clearer margin, but the two athletes were relentless and full of heart, everything their inspiration the legend embodied.
