British light heavyweight Buatsi secured a victory yet disappointing beginning to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a close ten-round contest at the Co-op Live Arena.
But Parker had his moments, delivering effective individual punches in a fight where the approaches never quite clicked, with constant grabbing marring the fight.
The officials scored it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my best display but what defines champions? They prevail," the victor commented in the arena as he was faced boos from the crowd.
The British fighter got back to winning after his first professional defeat - an thrilling contest with Callum Smith in last winter - to claim a 20th career victory.
Various analysts thought Parker, 31, deserved the win but the contender experienced the second defeat of his 28-fight professional journey.
Buatsi Claims Win in Uneventful Encounter
His career development has slowed in recent times through contract problems and considerable time of inactivity.
Once tipped as the future of British boxing, he now stands trying to achieve expectations - maybe in what appears to be a last chance - under recent support.
He began cautiously, with both competitors willing to overcommit in a tentative initial rounds.
Parker, whose only previous defeat came at super-middleweight against John Ryder in 2022 after suffering a hand injury during the bout, was competing in only his second bout at light heavyweight.
By the fight's midpoint, Parker had made it competitive, making life awkward for the favorite, who worked behind a tight guard to barely take the cleaner stanzas.
The spectators' acceptance diminished because of constant clinching, with the challenger slipping to the canvas multiple occasions during clinches.
The underdog finished the stronger, but several stanzas were hard to judge. Nevertheless, previous titleholder Carl Frampton - commentating on the broadcast network - had it strongly leaning for Parker, giving Buatsi just a single round.
The victor advances, but with the caliber of hard hitter Benavidez, and Eastern European fighter Bivol leading the category, the road to world glory - based on this performance - still appears challenging.
Hatton Memorial Inspires Local Rivalry Battle
In the co-main event, Lyndon Arthur beat Bradley Rea by divided decision in a excellent local rivalry battle to secure the continental title.
The venue grew hushed for a deeply poignant memorial before the fight as ten bells tolled in memory of local hero Ricky Hatton, who succumbed at age 46 in September.
It was the initial significant broadcast match card in the location since Hatton's death. As the final chime disappeared, the quiet became a chant of "there's only one Hatton".
The action during the bout matched the sentiment. Arthur was floored by a powerful punch flush on the face in the early round, rising shakily to his position on the referee's count.
But the red-colored attire of Arthur soon pressed ahead again. Across the ring, the opponent - in rival City blue - was marked up soon, noticeable damage forming under his eye as the pair exchanged hard punches.
The challenger, 27, delivered effective strikes but the champion, thirty-four, responded in kind with stinging uppercuts as the pace hardly diminished over 12 rounds.
Arthur edged the verdict with official scores of draw, close margin and clearer margin, but each competitor were relentless and courageous, exactly what their hero the legend stood for.
