UK light-heavyweight Buatsi secured a victory yet disappointing debut to his career under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output likely gained him a judges' verdict in a tight ten-round fight at the boxing arena.
But Parker landed significant shots, connecting with powerful clean blows in a fight where the styles didn't complement each other, with constant grabbing spoiling the fight.
Two judges scored it 96-94 to the winner, with the final judge a even score.
"It wasn't my finest display but how do champions respond? They win," the victor said in the arena as he was faced negative reactions from the crowd.
The Londoner got back to winning after his maiden career setback - an epic battle with Callum Smith in last winter - to claim a twentieth professional win.
Several boxing experts believed Parker, thirty-one, should have been awarded the victory but the British boxer endured the second loss of his 28-bout career.
Buatsi Secures Victory in Uneventful Affair
The fighter's advancement has stalled in recent times through management issues and considerable time of lack of fights.
Earlier forecast as the future of the British fight scene, he now finds himself trying to realize his potential - possibly in what feels like a last chance - under new promotional backing.
He started carefully, with the two boxers willing to overcommit in a tentative early stages.
Parker, whose only previous defeat came at super middleweight against John Ryder in 2022 after breaking his hand during the bout, was competing in only his second appearance at light heavyweight.
By the middle rounds, Parker had made it competitive, creating difficulties for Buatsi, who utilized a tight guard to edge the more effective rounds.
The audience's tolerance decreased amid frequent holding, with Parker falling to the floor multiple occasions during close exchanges.
The underdog ended stronger, but many rounds were challenging to assess. Nevertheless, previous titleholder the boxing analyst - working with the broadcast network - had it particularly wide for Parker, awarding Buatsi just only one stanza.
The victor moves on, but with the presence of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - on this evidence - still seems difficult.
Hatton Homage Fuels All-Manchester Battle
In the secondary fight, Arthur overcame Bradley Rea by close verdict in a outstanding local rivalry battle to capture the European light-heavyweight championship.
The arena grew hushed for a extremely emotional tribute prior to the bout as 10 bells sounded in memory of local hero Ricky Hatton, who succumbed at age 46 in last month.
It was the premier televised match card in the location since Hatton's death. As the concluding sound ended, the stillness gave way to a chant of "there's just one Hatton".
The competition inside the ropes equaled the emotion. The eventual winner was sent to the canvas by a powerful punch squarely on the jaw in the second round, getting up unsteadily to his position on the eight count.
But the traditional red shorts of Arthur soon pressed ahead again. Across the ring, Rea - in competitive blue - was damaged soon, heavy swelling forming under his face as the duo exchanged punishing blows.
The challenger, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with stinging uppercuts as the intensity hardly diminished over 12 rounds.
The victor narrowly won the decision with scoring tallies of draw, close margin and clearer margin, but both fighters were persistent and brave, exactly what their hero Hatton represented.
