British light-heavyweight Buatsi earned a win 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 punch output appeared to earn him a judges' verdict in a competitive 10-round bout at the Co-op Live Arena.
But the challenger landed significant shots, connecting with powerful single shots in a match where the styles didn't complement each other, with excessive holding spoiling the contest.
Two judges had it 96-94 for to Buatsi, with the final judge a even score.
"It wasn't my greatest display but what defines champions? They win," Buatsi stated in the ring as he was faced disapproval from the audience.
The British fighter returned to winning ways after his maiden career setback - an memorable fight with Callum Smith in last winter - to earn a 20th career victory.
Some ringside observers believed Parker, 31, merited the decision but the contender endured the second defeat of his 28-bout career.
The Champion Claims Win in Dull Encounter
His career development has stalled in the past few years through contract problems and long spells of lack of fights.
Once tipped as the future of UK boxing, he now stands trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under new promotional backing.
He began cautiously, with neither fighter prepared to take risks in a cagey initial rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after breaking his hand during the bout, was competing in only his second bout at the higher weight class.
By the halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who worked behind a solid defense to narrowly win the more effective stanzas.
The spectators' acceptance diminished during regular grabbing, with the challenger slipping to the canvas multiple occasions 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 significantly in favor for the challenger, scoring for Buatsi just a single round.
Buatsi advances, but with the presence of heavy hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Hatton Homage Inspires Local Rivalry Battle
In the supporting bout, Arthur beat Bradley Rea by close verdict in a terrific all-Manchester contest to secure the European light-heavyweight championship.
The stadium became quiet for a extremely emotional tribute prior to the bout as 10 bells rang in honor of local hero Ricky Hatton, who died 46 years old in recently.
It was the initial significant broadcast match card in the location since the passing of Hatton. As the final chime ended, the silence became a shout of "only one Hatton".
The action within the ring reflected the sentiment. The eventual winner was floored by a left hook directly to the chin in the second round, getting up unsteadily to his footing on the count of eight.
But the traditional red attire of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was marked up soon, heavy swelling developing under his eye as the fighters traded powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, 34, responded in kind with stinging uppercuts as the intensity rarely dropped over 12 rounds.
The victor narrowly won the decision with judges scorecards of draw, 115-113 and clearer margin, but the two athletes were relentless and full of heart, exactly what their inspiration Hatton stood for.
