UK light heavyweight Buatsi earned a win yet underwhelming debut to life under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a split decision in a close 10-round contest at the boxing arena.
But the challenger had his moments, connecting with powerful single shots in a match where the approaches never quite clicked, with excessive holding disrupting the action.
Two judges scored it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my best performance but what defines champions? They win," the victor stated in the ringside as he was greeted with negative reactions from the crowd.
The Londoner got back to winning after his maiden career setback - an thrilling contest with his previous opponent in February - to earn a 20th career victory.
Some ringside observers believed the challenger, 31, merited the decision but the British boxer suffered the second loss of his 28-fight career.
Buatsi Secures Win in Dull Encounter
His career development has slowed in the past few years through promotional disputes and long spells of inactivity.
Previously predicted as the next star of British boxing, he now finds himself trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under fresh management.
He opened tentatively, with both competitors willing to overcommit in a cagey initial rounds.
Parker, whose sole prior loss came at super middleweight against John Ryder in two years ago after suffering a hand injury in the contest, was competing in only his second appearance at light heavyweight.
By the middle rounds, the underdog had made it competitive, creating difficulties for the favorite, who operated with a protective stance to narrowly win the more effective stanzas.
The crowd's patience diminished during regular grabbing, with Parker slipping to the canvas various instances during close exchanges.
Parker finished the stronger, but several stanzas were difficult to score. Nevertheless, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, awarding Buatsi just a single round.
Buatsi progresses, but with the presence of heavy hitter Benavidez, and Russian star Bivol ruling the division, the journey to titles - judging by this showing - still seems difficult.
Ricky Hatton Tribute Fuels Local Rivalry Fight
In the supporting bout, Lyndon Arthur defeated Bradley Rea by divided decision in a outstanding all-Manchester fight to secure the continental championship.
The venue became quiet for a extremely emotional homage prior to the bout as 10 bells rang in honor of local hero Ricky Hatton, who died 46 years old in September.
It was the first major televised match card in the urban center since Hatton's death. As the concluding sound faded, the silence transitioned to a shout of "there's only one Hatton".
The action inside the ropes reflected the feeling. The eventual winner was sent to the canvas by a significant blow flush on the jaw in the second round, getting up unsteadily to his position on the referee's count.
But the Manchester United-red attire of Arthur soon pressed ahead again. On the opposite side, Rea - in opposing blue - was marked up soon, significant bruising forming under his eye as the duo landed powerful shots.
The challenger, twenty-seven, landed power punches but Arthur, 34, matched the intensity with effective uppercuts as the pace rarely dropped over twelve rounds.
Arthur barely secured the verdict with judges scorecards of even score, 115-113 and clearer margin, but both fighters were persistent and courageous, everything their hero the legend stood for.
