British light-heavyweight Buatsi secured a victory yet underwhelming start to his career under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a split decision in a tight 10-round contest at the Manchester venue.
But Parker had his moments, delivering effective individual punches in a fight where the approaches didn't complement each other, with constant grabbing spoiling the action.
The scoring judges had it 96-94 in favor to the winner, with the third a even score.
"It wasn't my best performance but what do champions do? They win," the victor commented in the arena as he was faced disapproval from the audience.
The British fighter bounced back after his initial pro loss - an thrilling contest with Callum Smith in February - to claim a twentieth professional win.
Various analysts thought Parker, 31, should have been awarded the decision but the Derbyshire fighter endured the second loss of his 28-match career.
The Champion Claims Triumph in Dull Affair
His career development has plateaued in recent years through promotional disputes and extended periods of lack of fights.
Once tipped as the next star of UK boxing, he now finds himself trying to realize his potential - perhaps in what seems like a last chance - under new promotional backing.
He started carefully, with the two boxers willing to take risks in a cagey initial rounds.
Parker, whose only previous defeat came at super-middleweight against John Ryder in 2022 after damaging his hand in the contest, was making just his second bout at the higher weight class.
By the fight's midpoint, the underdog had kept it close, creating difficulties for the favorite, who operated with a solid defense to barely take the better rounds.
The audience's tolerance diminished amid regular grabbing, with Parker slipping to the canvas multiple occasions during clinches.
Parker finished the stronger, but many rounds were difficult to score. Although, ex-champion Carl Frampton - providing analysis for Dazn - had it particularly wide for Parker, scoring for Buatsi just a single round.
The victor moves on, but with the likes of hard hitter Benavidez, and Russian star Bivol ruling the division, the journey to titles - judging by this showing - still looks steep.
Hatton Homage Motivates All-Manchester Contest
In the secondary fight, Arthur defeated Rea by divided decision in a terrific local rivalry contest to win the European light heavyweight championship.
The stadium fell silent for a profoundly moving memorial ahead of the contest as a bell ceremony rang in honor of the city's native Ricky Hatton, who died at age 46 in September.
It was the initial significant broadcast fight night in the urban center since Hatton's death. As the last bell ended, the quiet became a roar of "only one Ricky Hatton".
The action within the ring matched the feeling. The eventual winner was floored by a left hook flush on the chin in the early round, rising shakily to his footing on the referee's count.
But the red-colored equipment of Arthur soon advanced again. Across the ring, the opponent - in competitive blue - was injured early, noticeable damage developing under his face as the duo exchanged punishing blows.
The challenger, 27, landed power punches but the champion, 34, responded in kind with powerful upward punches as the pace rarely dropped over 12 rounds.
Arthur narrowly won the decision with official scores of draw, close margin and clearer margin, but both fighters were determined and brave, everything their inspiration Hatton embodied.
