UK light heavyweight Buatsi earned a win yet disappointing beginning to his career under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a split decision in a competitive ten-round contest at the Manchester venue.
But the challenger found success, landing some telling individual punches in a match where the styles never quite clicked, with excessive holding marring the fight.
The scoring judges had it 96-94 for to the winner, with the final judge a even score.
"It wasn't my best showing but what defines champions? They succeed," Buatsi stated in the ring as he was greeted with negative reactions from the spectators.
The Londoner bounced back after his initial pro loss - an memorable fight with his previous opponent in February - to claim a 20th career victory.
Various analysts believed Parker, thirty-one, should have been awarded the decision but the Derbyshire fighter endured the second setback of his 28-bout professional journey.
The Champion Earns Win in Uneventful Affair
His career development has plateaued in the past few years through promotional disputes and extended periods of lack of fights.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to achieve expectations - possibly in what appears to be a final roll of the dice - under recent support.
He opened tentatively, with the two boxers prepared to take risks in a cagey opening few rounds.
The challenger, 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 fight at light-heavyweight.
By the halfway stage, Parker had kept it close, making life awkward for the favorite, who operated with a tight guard to edge the cleaner periods.
The audience's tolerance diminished amid frequent holding, with Parker slipping to the canvas various instances during grappling.
Parker closed well, but many rounds were hard to judge. Although, previous titleholder Carl Frampton - working with the broadcast network - had it strongly leaning for Parker, giving Buatsi just only one stanza.
Buatsi moves on, but with the caliber 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 Memorial Fuels All-Manchester Battle
In the secondary fight, Lyndon Arthur beat Rea by close verdict in a excellent all-Manchester contest to secure the European light-heavyweight championship.
The stadium fell silent for a deeply poignant tribute prior to the bout as 10 bells sounded in memory of local hero Ricky Hatton, who died at age 46 in September.
It was the first major televised boxing event in the location since Hatton's passing. As the final chime faded, the silence became a chant of "there's only one Hatton".
The action within the ring reflected the sentiment. Arthur was sent to the canvas by a powerful punch flush on the jaw in the second round, standing uncertainly to his feet on the referee's count.
But the Manchester United-red equipment of Arthur soon advanced again. From the other corner, Rea - in opposing blue - was damaged soon, heavy swelling developing under his face as the fighters traded punishing blows.
The challenger, twenty-seven, landed power punches but Arthur, 34, responded in kind with powerful upward punches as the action hardly diminished over 12 rounds.
Arthur narrowly won the verdict with scoring tallies of even score, narrow lead and 115-112, but the two athletes were relentless and full of heart, exactly what their inspiration the legend embodied.
