UK light-heavyweight Buatsi made a winning yet underwhelming debut to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a split decision in a tight ten-round contest at the boxing arena.
But Parker landed significant shots, delivering effective clean blows in a match where the approaches didn't complement each other, with constant grabbing spoiling the fight.
The scoring judges judged it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my best display but what defines champions? They win," Buatsi stated in the ringside as he was met by negative reactions from the audience.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in February - to earn a 20th career victory.
Various analysts believed Parker, 31, deserved the victory but the contender suffered the second loss of his 28-fight career.
The Champion Earns Victory in Uneventful Affair
Buatsi's progress has slowed in the past few years through contract problems and long spells of inactivity.
Once tipped as the next star of British boxing, he now finds himself trying to realize his potential - maybe in what feels like a ultimate opportunity - under fresh management.
He started carefully, with neither fighter prepared to take risks in a calculated initial rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in 2022 after damaging his hand mid-fight, was participating in his second bout at the higher weight class.
By the middle rounds, Parker had kept it close, creating difficulties for the favorite, who utilized a protective stance to narrowly win the more effective stanzas.
The crowd's patience decreased amid constant clinching, with the challenger slipping to the canvas several times during close exchanges.
Parker finished the stronger, but several stanzas were challenging to assess. However, ex-champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for the challenger, giving Buatsi just one round.
The victor progresses, but with the likes of heavy hitter Benavidez, and Russian star Bivol dominating the weight class, the journey to titles - judging by this showing - still seems difficult.
Ricky Hatton Memorial Motivates Manchester Derby Contest
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a terrific all-Manchester fight to secure the European light heavyweight belt.
The stadium fell silent for a extremely emotional homage before the fight as 10 bells rang in remembrance of local hero Hatton, who died 46 years old in recently.
It was the premier televised fight night in the city since the passing of Hatton. As the final chime faded, the silence became a roar of "there's only one Ricky Hatton".
The action inside the ropes reflected the emotion. The eventual winner was floored by a significant blow directly to the face in the initial stage, standing uncertainly to his position on the count of eight.
But the red-colored equipment of Arthur soon pressed ahead again. From the other corner, Rea - in competitive blue - was injured soon, significant bruising appearing under his face as the duo traded powerful shots.
Rea, 27, connected with strong blows but the champion, 34, matched the intensity with effective uppercuts as the action seldom decreased over 12 rounds.
The victor barely secured the verdict with official scores of even score, close margin and 115-112, but each competitor were relentless and courageous, everything their idol Hatton embodied.
