UK light heavyweight Buatsi made a winning yet unimpressive beginning to his career under new promoters with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a majority decision in a close 10-round bout at the Co-op Live Arena.
But the challenger found success, connecting with powerful single shots in a match where the approaches never quite clicked, with frequent clinching marring the contest.
The scoring judges had it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my best display but what defines champions? They succeed," the victor said in the ring as he was greeted with disapproval from the crowd.
The British fighter got back to winning after his maiden career setback - an epic battle with Callum Smith in February - to claim a twentieth professional win.
Some ringside observers believed Parker, 31, deserved the decision but the contender suffered the second loss of his 28-fight professional journey.
His career development has stalled in recent years through contract problems and long spells of lack of fights.
Earlier forecast as the next star of UK boxing, he now stands trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under new promotional backing.
He began cautiously, with the two boxers prepared to be aggressive in a tentative initial rounds.
The challenger, 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 bout at the higher weight class.
By the middle rounds, Parker had made it competitive, making life awkward for Buatsi, who worked behind a protective stance to narrowly win the cleaner rounds.
The crowd's patience wore thin amid constant clinching, with the challenger going down several times during grappling.
Parker ended stronger, but many rounds were challenging to assess. Although, previous titleholder Carl Frampton - working with Dazn - had it particularly wide for the challenger, giving Buatsi just only one stanza.
Buatsi progresses, but with the caliber of power puncher Benavidez, and Russian champion Bivol ruling the division, the journey to titles - on this evidence - still seems difficult.
In the secondary fight, Lyndon Arthur defeated Rea by split-decision in a excellent all-Manchester fight to capture the continental belt.
The venue grew hushed for a profoundly moving memorial ahead of the contest as ten bells rang in remembrance of Manchester's own Hatton, who passed away aged 46 in September.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the concluding sound ended, the quiet became a roar of "there's just one Ricky Hatton".
The fighting within the ring reflected the sentiment. The eventual winner was floored by a significant blow squarely on the chin in the early round, standing uncertainly to his footing on the eight count.
But the red-colored equipment of the fighter soon pressed ahead again. On the opposite side, Rea - in competitive blue - was marked up quickly, heavy swelling appearing under his face as the pair traded powerful shots.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, matched the intensity with stinging uppercuts as the intensity seldom decreased over 12 rounds.
The victor narrowly won the result with official scores of draw, close margin and clearer margin, but the two athletes were relentless and courageous, everything their hero the legend represented.
A digital wellness coach and productivity expert with over a decade of experience helping professionals optimize their workflow.