British light heavyweight Buatsi made a winning yet unimpressive beginning to life under new promoters with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a split decision in a competitive 10-round fight at the Co-op Live Arena.
But Parker found success, connecting with powerful clean blows in a contest where the techniques failed to mesh, with constant grabbing disrupting the contest.
The officials had it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my best showing but what do champions do? They win," the victor said in the arena as he was met by disapproval from the spectators.
The British fighter got back to winning after his initial pro loss - an memorable fight with Callum Smith in February - to secure a 20th pro success.
Several boxing experts believed the challenger, thirty-one, deserved the victory but the British boxer endured the second setback of his 28-bout career.
Buatsi Earns Victory in Dull Match
His career development has plateaued in recent times through promotional disputes and considerable time of inactivity.
Previously predicted as the rising talent of the British fight scene, he now stands trying to achieve expectations - perhaps in what appears to be a final roll of the dice - under recent support.
He began cautiously, with the two boxers ready to take risks in a cagey initial rounds.
Parker, whose only previous defeat came at super middleweight against John Ryder in 2022 after breaking his hand in the contest, was competing in only his second bout at the higher weight class.
By the halfway stage, Parker had kept it close, making life awkward for the favorite, who operated with a solid defense to barely take the better rounds.
The spectators' acceptance diminished amid regular grabbing, with Parker going down several times during close exchanges.
The underdog closed well, but many rounds were difficult to score. Although, previous titleholder the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, giving Buatsi just one round.
Buatsi advances, but with the presence of power puncher David Benavidez, and Russian star Bivol ruling the division, the road to world glory - based on this performance - still seems difficult.
Ricky Hatton Homage Motivates All-Manchester Fight
In the co-main event, Arthur defeated Bradley Rea by split-decision in a terrific all-Manchester contest to secure the continental belt.
The stadium became quiet for a extremely emotional memorial prior to the bout as a bell ceremony rang in memory of Manchester's own Hatton, who died aged 46 in last month.
It was the premier televised match card in the location since the passing of Hatton. As the concluding sound disappeared, the quiet gave way to a roar of "there's only one Hatton".
The competition during the bout equaled the feeling. The eventual winner was sent to the canvas by a left hook flush on the chin in the initial stage, getting up unsteadily to his position on the count of eight.
But the traditional red shorts of Arthur soon advanced again. Across the ring, Rea - in competitive blue - was marked up soon, heavy swelling developing under his eye as the duo exchanged powerful shots.
Rea, 27, connected with strong blows but the champion, thirty-four, matched the intensity with stinging uppercuts as the pace hardly diminished over twelve rounds.
The victor narrowly won the result with scoring tallies of 114-114, 115-113 and wider gap, but the two athletes were persistent and brave, exactly what their inspiration the legend represented.
