British light heavyweight Buatsi secured a victory yet unimpressive beginning to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a close 10-round bout at the Co-op Live Arena.
But Parker had his moments, landing some telling clean blows in a contest where the approaches didn't complement each other, with excessive holding disrupting the action.
The officials judged it 96-94 for to Buatsi, with the final judge a even score.
"It wasn't my best performance but what do champions do? They prevail," the victor said in the arena as he was faced boos from the spectators.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with Callum Smith in last winter - to earn a 20th career victory.
Various analysts believed the challenger, 31, merited the decision but the contender experienced the second defeat of his 28-fight professional journey.
The Champion Claims Triumph in Dull Affair
His career development has stalled in recent years through contract problems and considerable time of inactivity.
Previously predicted as the next star of British boxing, he now finds himself trying to realize his potential - maybe in what feels like a final roll of the dice - under new promotional backing.
He started carefully, with both competitors ready to be aggressive in a tentative initial rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after damaging his hand in the contest, was competing in only his second appearance at the higher weight class.
By the halfway stage, the underdog had kept it close, creating difficulties for the favorite, who operated with a protective stance to narrowly win the cleaner stanzas.
The spectators' acceptance wore thin during regular grabbing, with Parker going down multiple occasions during clinches.
Parker finished the stronger, but several stanzas were challenging to assess. Nevertheless, former world champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, giving Buatsi just a single round.
The victor moves on, but with the presence of power puncher Benavidez, and Russian champion Bivol leading the category, the road to world glory - judging by this showing - still looks steep.
Ricky Hatton Homage Inspires Local Rivalry Contest
In the supporting bout, Arthur overcame Rea by close verdict in a terrific Manchester vs Manchester fight to win the European light heavyweight belt.
The stadium fell silent for a profoundly moving tribute before the fight as ten bells tolled in remembrance of local hero Ricky Hatton, who died aged 46 in recently.
It was the first major televised match card in the location since Hatton's death. As the last bell ended, the stillness became a roar of "there's only one Hatton".
The competition within the ring equaled the sentiment. The eventual winner was knocked down by a left hook squarely on the chin in the second round, standing uncertainly to his feet on the count of eight.
But the traditional red shorts of Arthur soon advanced again. From the other corner, Rea - in rival City blue - was marked up soon, heavy swelling appearing under his orbital area as the fighters traded hard punches.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, responded in kind with powerful upward punches as the action rarely dropped over twelve rounds.
Arthur narrowly won the result with official scores of draw, narrow lead and 115-112, but both fighters were determined and brave, everything their idol Hatton stood for.
