British light heavyweight Buatsi earned a win yet disappointing debut to life under new promoters with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a judges' verdict in a competitive 10-round contest at the Manchester venue.
But the challenger found success, connecting with powerful clean blows in a fight where the approaches failed to mesh, with excessive holding marring the fight.
The officials judged it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my greatest showing but how do champions respond? They win," the victor commented in the ringside as he was met by boos from the spectators.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in last winter - to earn a 20th career victory.
Various analysts thought the challenger, thirty-one, merited the victory but the Derbyshire fighter endured the second defeat of his 28-bout career.
The Champion Secures Victory in Slow Affair
His career development has slowed in recent years through contract problems and considerable time of inactivity.
Once tipped as the rising talent of British boxing, he now stands trying to realize his potential - possibly in what appears to be a ultimate opportunity - under fresh management.
He started carefully, with neither fighter ready to take risks in a tentative initial rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in 2022 after breaking his hand in the contest, was making just his second appearance at the higher weight class.
By the fight's midpoint, the underdog had kept it close, making life awkward for the favorite, who utilized a protective stance to edge the more effective rounds.
The spectators' acceptance diminished during regular grabbing, with the challenger slipping to the canvas various instances during grappling.
Parker finished the stronger, but several stanzas were challenging to assess. Although, ex-champion Carl Frampton - working with Dazn - had it strongly leaning for Parker, giving Buatsi just one round.
The victor moves on, but with the likes of power puncher David Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - on this evidence - still looks steep.
Ricky Hatton Tribute Fuels Manchester Derby Fight
In the secondary fight, Lyndon Arthur overcame Bradley Rea by divided decision in a excellent Manchester vs Manchester contest to win the European light-heavyweight belt.
The stadium grew hushed for a deeply poignant memorial before the fight as a bell ceremony tolled in honor of Manchester's own Ricky Hatton, who passed away aged 46 in September.
It was the premier televised boxing event in the location since Hatton's passing. As the last bell disappeared, the quiet transitioned to a shout of "only one Ricky Hatton".
The fighting within the ring reflected the sentiment. Arthur was sent to the canvas by a left hook flush on the chin in the initial stage, getting up unsteadily to his footing on the referee's count.
But the Manchester United-red equipment of the fighter soon advanced again. Across the ring, Rea - in competitive blue - was damaged quickly, significant bruising developing under his eye as the pair landed hard punches.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, responded in kind with powerful upward punches as the action rarely dropped over the full distance.
Arthur edged the verdict with official scores of draw, narrow lead and wider gap, but each competitor were determined and brave, everything their idol the legend embodied.
