UK light heavyweight Buatsi made a winning yet disappointing debut to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a tight ten-round fight at the boxing arena.
But Parker had his moments, landing some telling individual punches in a match where the approaches never quite clicked, with excessive holding spoiling the action.
The scoring judges had it 96-94 in favor to Buatsi, with the third a 95-95.
"It wasn't my greatest showing but what defines champions? They prevail," the victor commented in the ringside as he was faced disapproval from the audience.
The Londoner got back to winning after his first professional defeat - an thrilling contest with Callum Smith in last winter - to secure a twentieth professional win.
Various analysts believed Parker, thirty-one, deserved the victory but the British boxer experienced the second setback of his 28-fight career.
Buatsi Earns Win in Dull Match
His career development has slowed in the past few years through promotional disputes and long spells of inactivity.
Once tipped as the future of UK boxing, he now stands trying to achieve expectations - possibly in what seems like a last chance - under new promotional backing.
He opened tentatively, with both competitors willing to overcommit in a cagey early stages.
The challenger, whose single earlier setback came at super middleweight against his former opponent in two years ago after damaging his hand in the contest, was participating in his second appearance at the higher weight class.
By the middle rounds, Parker had stayed in contention, creating difficulties for Buatsi, who worked behind a tight guard to narrowly win the cleaner periods.
The spectators' acceptance wore thin because of regular grabbing, with the challenger going down several times during clinches.
The underdog ended stronger, but multiple periods were difficult to score. Although, previous titleholder the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the caliber of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - based on this performance - still looks steep.
Hatton Homage Inspires Local Rivalry Contest
In the co-main event, Arthur overcame Bradley Rea by divided decision in a terrific Manchester vs Manchester battle to secure the European light heavyweight championship.
The venue became quiet for a profoundly moving memorial prior to the bout as a bell ceremony rang in remembrance of the city's native Ricky Hatton, who succumbed aged 46 in recently.
It was the first major televised fight night in the city since Hatton's death. As the final chime faded, the quiet transitioned to a chant of "there's only one Ricky Hatton".
The competition within the ring reflected the feeling. Arthur was knocked down by a powerful punch directly to the chin in the second round, standing uncertainly to his feet on the count of eight.
But the red-colored shorts of the fighter soon advanced again. Across the ring, the opponent - in rival City blue - was marked up early, significant bruising developing under his orbital area as the duo exchanged hard punches.
The challenger, 27, connected with strong blows but the champion, 34, matched the intensity with powerful upward punches as the pace seldom decreased over twelve rounds.
Arthur edged the result with judges scorecards of 114-114, 115-113 and 115-112, but both fighters were relentless and courageous, all the qualities their hero Hatton embodied.
