British light heavyweight Buatsi made a winning yet unimpressive beginning to his career under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a split decision in a tight 10-round fight at the Manchester venue.
But the challenger had his moments, landing some telling clean blows in a contest where the techniques didn't complement each other, with excessive holding marring the fight.
The scoring judges judged it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my best showing but what defines champions? They succeed," the victor stated in the ring as he was greeted with 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 earn a 20th pro success.
Some ringside observers believed Parker, thirty-one, merited the decision but the Derbyshire fighter suffered the second setback of his 28-fight career.
The Champion Earns Win in Slow Match
The fighter's advancement has plateaued in recent times through contract problems and long spells of lack of fights.
Once tipped as the next star of UK boxing, he now is positioned trying to realize his potential - maybe in what appears to be a final roll of the dice - under new promotional backing.
He began cautiously, with neither fighter ready to take risks in a calculated early stages.
Parker, whose only previous defeat came at super middleweight against John Ryder in two years ago after breaking his hand in the contest, was competing in only his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for the favorite, who utilized a solid defense to barely take the more effective rounds.
The audience's tolerance decreased amid regular grabbing, with Parker slipping to the canvas various instances during close exchanges.
Parker ended stronger, but several stanzas were hard to judge. However, previous titleholder the boxing analyst - providing analysis for Dazn - had it strongly leaning for the challenger, giving Buatsi just only one stanza.
Buatsi moves on, but with the likes of heavy hitter Benavidez, and Russian champion Bivol dominating the weight class, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Tribute Motivates Local Rivalry Contest
In the supporting bout, Arthur overcame Bradley Rea by close verdict in a excellent Manchester vs Manchester contest to win the continental belt.
The arena became quiet for a deeply poignant memorial ahead of the contest as ten bells tolled in honor of Manchester's own Ricky Hatton, who passed away at age 46 in last month.
It was the first major televised boxing event in the urban center since Hatton's death. As the final chime faded, the quiet transitioned to a shout of "there's only one Ricky Hatton".
The fighting within the ring equaled the feeling. Arthur was sent to the canvas by a powerful punch directly to the jaw in the early round, standing uncertainly to his feet on the count of eight.
But the traditional red attire of Arthur soon came forward again. On the opposite side, Rea - in rival City blue - was injured quickly, significant bruising appearing under his eye as the fighters exchanged punishing blows.
Rea, 27, connected with strong blows but the champion, 34, matched the intensity with stinging uppercuts as the pace seldom decreased over the full distance.
Arthur barely secured the decision with official scores of even score, close margin and 115-112, but the two athletes were persistent and full of heart, everything their hero the legend stood for.
