British light heavyweight Buatsi secured a victory yet unimpressive start to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a judges' verdict in a competitive ten-round contest at the Co-op Live Arena.
But the challenger landed significant shots, connecting with powerful clean blows in a fight where the approaches never quite clicked, with frequent clinching disrupting the action.
Two judges had it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my best showing but how do champions respond? They succeed," the victor said in the arena as he was greeted with negative reactions from the spectators.
The Londoner got back to winning after his initial pro loss - an memorable fight with his previous opponent in February - to claim a 20th pro success.
Several boxing experts thought Parker, 31, deserved the victory but the Derbyshire fighter endured the second setback of his 28-bout career.
Buatsi Secures Victory in Slow Affair
His career development has plateaued in recent times through promotional disputes and extended periods of lack of fights.
Earlier forecast as the next star of UK boxing, he now is positioned trying to realize his potential - maybe in what seems like a last chance - under recent support.
He began cautiously, with the two boxers prepared to be aggressive in a cagey initial rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was making just his second bout at the higher weight class.
By the halfway stage, the underdog had kept it close, causing problems for Buatsi, who utilized a tight guard to edge the better rounds.
The audience's tolerance wore thin because of frequent holding, with Parker going down various instances during clinches.
Parker finished the stronger, but many rounds were challenging to assess. However, former world champion Carl Frampton - working with the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
Buatsi advances, but with the presence of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still appears challenging.
Ricky Hatton Homage Inspires Local Rivalry Fight
In the secondary fight, Lyndon Arthur overcame Bradley Rea by divided decision in a excellent local rivalry contest to win the European light-heavyweight belt.
The stadium fell silent for a deeply poignant memorial before the fight as a bell ceremony tolled in remembrance of Manchester's own Hatton, who succumbed at age 46 in last month.
It was the first major televised fight night in the city since the passing of Hatton. As the concluding sound ended, the stillness became a shout of "there's just one Ricky Hatton".
The competition within the ring equaled the sentiment. The eventual winner was knocked down by a significant blow directly to the jaw in the second round, getting up unsteadily to his feet on the count of eight.
But the red-colored equipment of Arthur soon came forward again. On the opposite side, Rea - in rival City blue - was marked up early, noticeable damage appearing under his face as the duo exchanged powerful shots.
The challenger, twenty-seven, landed power punches but the champion, 34, responded in kind with powerful upward punches as the action hardly diminished over 12 rounds.
Arthur edged the verdict with judges scorecards of even score, narrow lead and 115-112, but both fighters were determined and full of heart, everything their hero Hatton embodied.
