British light heavyweight Buatsi made a winning yet unimpressive start to life under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a judges' verdict in a competitive 10-round bout at the Manchester venue.
But Parker had his moments, landing some telling clean blows in a contest where the techniques never quite clicked, with excessive holding spoiling the action.
The scoring judges judged it 96-94 to the winner, with the third a 95-95 draw.
"It wasn't my greatest performance but what do champions do? They win," the victor said in the ring as he was greeted with negative reactions from the crowd.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with Callum Smith in February - to claim a twentieth professional win.
Some ringside observers felt the challenger, thirty-one, should have been awarded the decision but the British boxer experienced the second setback of his 28-fight career.
Buatsi Secures Triumph in Dull Match
The fighter's advancement has plateaued in recent years through promotional disputes and long spells of inactivity.
Earlier forecast as the next star of the British fight scene, he now finds himself trying to realize his potential - possibly in what seems like a final roll of the dice - under recent support.
He began cautiously, with the two boxers willing to overcommit in a cagey early stages.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after suffering a hand injury during the bout, was participating in his second fight at light heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who worked behind a protective stance to narrowly win the cleaner rounds.
The spectators' acceptance diminished during constant clinching, with Parker slipping to the canvas various instances during close exchanges.
The underdog closed well, but many rounds were difficult to score. Although, previous titleholder the boxing analyst - providing analysis for Dazn - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
The victor progresses, but with the caliber of power puncher Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Memorial Fuels Manchester Derby Battle
In the supporting bout, Lyndon Arthur overcame Rea by divided decision in a excellent all-Manchester fight to capture the continental championship.
The arena grew hushed for a extremely emotional tribute prior to the bout as a bell ceremony tolled in memory of the city's native Hatton, who died 46 years old in September.
It was the premier televised boxing event in the urban center since the passing of Hatton. As the last bell disappeared, the silence became a chant of "only one Ricky Hatton".
The competition inside the ropes equaled the sentiment. The eventual winner was knocked down by a powerful punch squarely on the chin in the second round, standing uncertainly to his feet on the referee's count.
But the red-colored equipment of Arthur soon came forward again. On the opposite side, Rea - in competitive blue - was marked up early, heavy swelling developing under his eye as the fighters exchanged powerful shots.
Rea, 27, delivered effective strikes but the champion, 34, responded in kind with powerful upward punches as the pace rarely dropped over 12 rounds.
Arthur narrowly won the verdict with judges scorecards of draw, close margin and 115-112, but the two athletes were persistent and brave, exactly what their inspiration Hatton embodied.
