British light heavyweight Buatsi secured a victory yet unimpressive debut to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a majority decision in a competitive 10-round contest at the Manchester venue.
But the challenger found success, connecting with powerful individual punches in a contest where the approaches never quite clicked, with excessive holding disrupting the action.
Two judges judged it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest display but what do champions do? They succeed," the victor stated in the ringside as he was met by boos from the crowd.
The British fighter got back to winning after his maiden career setback - an memorable fight with his previous opponent in last winter - to claim a 20th pro success.
Several boxing experts felt the challenger, thirty-one, deserved the win but the contender endured the second setback of his 28-fight professional journey.
The Champion Claims Victory in Uneventful Affair
His career development has stalled in the past few years through management issues and long spells of inactivity.
Earlier forecast as the future of British boxing, he now stands trying to achieve expectations - possibly in what feels like a last chance - under recent support.
He started carefully, with both competitors willing to take risks in a cagey opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after suffering a hand injury in the contest, was participating in his second bout at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for the favorite, who worked behind a solid defense to narrowly win the more effective periods.
The crowd's patience wore thin during frequent holding, with the challenger slipping to the canvas several times during clinches.
Parker ended stronger, but many rounds were challenging to assess. However, former world champion Carl Frampton - commentating on Dazn - had it significantly in favor for the challenger, awarding Buatsi just one round.
Buatsi advances, but with the likes of hard hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Homage Inspires All-Manchester Contest
In the supporting bout, Arthur overcame Rea by close verdict in a terrific all-Manchester fight to win the European light-heavyweight title.
The arena fell silent for a deeply poignant homage before the fight as 10 bells sounded in memory of the city's native Hatton, who died aged 46 in September.
It was the premier televised boxing event in the city since the passing of Hatton. As the concluding sound disappeared, the silence transitioned to a roar of "there's only one Hatton".
The fighting during the bout equaled the feeling. Arthur was floored by a significant blow squarely on the jaw in the second round, getting up unsteadily to his footing on the eight count.
But the traditional red shorts of Arthur soon came forward again. From the other corner, the opponent - in opposing blue - was marked up early, heavy swelling forming under his orbital area as the fighters exchanged powerful shots.
Rea, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with effective uppercuts as the action hardly diminished over the full distance.
The victor narrowly won the verdict with official scores of 114-114, close margin and wider gap, but the two athletes were relentless and brave, all the qualities their hero Hatton represented.
