British light heavyweight Buatsi earned a win yet unimpressive debut to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a judges' verdict in a tight ten-round fight at the Manchester venue.
But Parker had his moments, landing some telling single shots in a fight where the styles failed to mesh, with constant grabbing disrupting the fight.
Two judges had it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my best performance but what defines champions? They prevail," Buatsi said in the ringside as he was met by disapproval from the spectators.
The Londoner returned to winning ways after his initial pro loss - an epic battle with his previous opponent in last winter - to secure a 20th career victory.
Some ringside observers thought Parker, thirty-one, merited the win but the British boxer endured the second setback of his 28-fight professional journey.
The Champion Earns Victory in Uneventful Affair
His career development has plateaued in the past few years through contract problems and long spells of lack of fights.
Previously predicted as the future of the British fight scene, he now stands trying to realize his potential - maybe in what feels like a ultimate opportunity - under recent support.
He opened tentatively, with both competitors prepared to overcommit in a calculated opening few rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was competing in only his second bout at light heavyweight.
By the halfway stage, Parker had made it competitive, causing problems for Buatsi, who operated with a protective stance to edge the cleaner stanzas.
The crowd's patience diminished amid constant clinching, with Parker going down several times during clinches.
The underdog finished the stronger, but multiple periods were hard to judge. Although, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for the challenger, giving Buatsi just one round.
The victor advances, but with the caliber of hard hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Hatton Memorial Inspires All-Manchester Fight
In the supporting bout, Lyndon Arthur beat Bradley Rea by split-decision in a excellent all-Manchester contest to win the European light-heavyweight championship.
The stadium fell silent for a deeply poignant memorial ahead of the contest as 10 bells rang in remembrance of local hero Ricky Hatton, who passed away aged 46 in last month.
It was the first major televised match card in the location since the passing of Hatton. As the last bell ended, the quiet gave way to a roar of "only one Ricky Hatton".
The action within the ring matched the feeling. Arthur was sent to the canvas by a powerful punch flush on the chin in the initial stage, rising shakily to his footing on the referee's count.
But the Manchester United-red attire of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was damaged quickly, heavy swelling forming under his orbital area as the fighters landed hard punches.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, matched the intensity with stinging uppercuts as the intensity hardly diminished over twelve rounds.
Arthur barely secured the verdict with scoring tallies of 114-114, narrow lead and wider gap, but both fighters were persistent and courageous, exactly what their hero the legend represented.
