UK light heavyweight Buatsi made a winning yet unimpressive start to life under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate appeared to earn him a split decision in a close ten-round fight at the Co-op Live Arena.
But Parker found success, landing some telling individual punches in a fight where the styles didn't complement each other, with excessive holding spoiling the contest.
Two judges had it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my greatest display but what defines champions? They prevail," Buatsi commented in the arena as he was met by negative reactions from the audience.
The British fighter got back to winning after his initial pro loss - an memorable fight with Callum Smith in last winter - to secure a 20th career victory.
Several boxing experts believed the challenger, 31, should have been awarded the victory but the British boxer suffered the second loss of his 28-fight professional journey.
The Champion Earns Victory in Uneventful Match
His career development has slowed in the past few years through promotional disputes and long spells of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now stands trying to achieve expectations - possibly in what appears to be a ultimate opportunity - under fresh management.
He opened tentatively, with the two boxers willing to be aggressive in a cagey opening few rounds.
Parker, whose single earlier setback came at super-middleweight against John Ryder in 2022 after suffering a hand injury in the contest, was making just his second fight at the higher weight class.
By the middle rounds, the underdog had made it competitive, causing problems for the favorite, who worked behind a protective stance to edge the cleaner periods.
The audience's tolerance wore thin during frequent holding, with Parker falling to the floor multiple occasions during close exchanges.
Parker ended stronger, but several stanzas were hard to judge. Nevertheless, previous titleholder Carl Frampton - working with the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
The victor advances, but with the caliber of hard hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - based on this performance - still appears challenging.
Ricky Hatton Memorial Motivates Manchester Derby Battle
In the secondary fight, Arthur overcame Rea by close verdict in a outstanding local rivalry contest to secure the European light heavyweight title.
The stadium grew hushed for a deeply poignant homage prior to the bout as a bell ceremony rang in honor of the city's native Ricky Hatton, who succumbed 46 years old in recently.
It was the initial significant broadcast fight night in the location since Hatton's passing. As the concluding sound disappeared, the stillness became a roar of "only one Hatton".
The competition within the ring reflected the sentiment. The eventual winner was floored by a left hook flush on the chin in the initial stage, getting up unsteadily to his feet on the referee's count.
But the Manchester United-red attire of the fighter soon pressed ahead again. On the opposite side, the opponent - in competitive blue - was marked up quickly, significant bruising appearing under his orbital area as the duo landed punishing blows.
Rea, 27, connected with strong blows but Arthur, 34, matched the intensity with effective uppercuts as the pace seldom decreased over the full distance.
The victor barely secured the result with scoring tallies of draw, close margin and clearer margin, but each competitor were relentless and courageous, everything their inspiration Hatton stood for.
