UK light heavyweight Buatsi secured a victory yet disappointing start to life under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a majority decision in a competitive 10-round bout at the Manchester venue.
But the challenger landed significant shots, connecting with powerful individual punches in a contest where the approaches never quite clicked, with frequent clinching marring the action.
The scoring judges had it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my greatest display but what do champions do? They prevail," Buatsi stated in the ring as he was faced boos from the audience.
The British fighter got back to winning after his maiden career setback - an epic battle with his previous opponent in last winter - to claim a 20th pro success.
Several boxing experts thought Parker, thirty-one, merited the victory but the contender experienced the second setback of his 28-fight professional journey.
The Champion Secures Triumph in Dull Encounter
The fighter's advancement has stalled in the past few years through contract problems and considerable time of lack of fights.
Previously predicted as the next star of the British fight scene, he now stands trying to realize his potential - possibly in what seems like a final roll of the dice - under recent support.
He started carefully, with neither fighter prepared to take risks in a calculated opening few rounds.
Parker, whose only previous defeat came at super-middleweight against his former opponent in 2022 after breaking his hand in the contest, was competing in only his second fight at the higher weight class.
By the middle rounds, Parker had stayed in contention, causing problems for the favorite, who operated with a protective stance to edge the better periods.
The crowd's patience wore thin during constant clinching, with the challenger slipping to the canvas several times during clinches.
The underdog ended stronger, but many rounds were challenging to assess. Although, former world champion Carl Frampton - commentating on Dazn - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
Buatsi progresses, but with the likes of heavy hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Hatton Homage Inspires Local Rivalry Contest
In the secondary fight, Lyndon Arthur overcame Rea by close verdict in a excellent Manchester vs Manchester contest to win the European light-heavyweight belt.
The arena became quiet for a deeply poignant homage before the fight as ten bells sounded in memory of Manchester's own Ricky Hatton, who died at age 46 in recently.
It was the premier televised match card in the city since Hatton's death. As the concluding sound disappeared, the silence became a roar of "there's just one Hatton".
The fighting within the ring matched the emotion. Arthur was floored by a left hook squarely on the face in the early round, rising shakily to his feet on the count of eight.
But the Manchester United-red equipment of Arthur soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was marked up early, heavy swelling developing under his face as the pair exchanged hard punches.
Rea, 27, delivered effective strikes but the champion, 34, matched the intensity with effective uppercuts as the action rarely dropped over the full distance.
The victor edged the verdict with judges scorecards of even score, close margin and wider gap, but both fighters were determined and full of heart, all the qualities their idol Hatton represented.
