UK light heavyweight Buatsi made a winning yet underwhelming start to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a majority decision in a competitive 10-round fight at the boxing arena.
But Parker landed significant shots, connecting with powerful single shots in a match where the techniques didn't complement each other, with frequent clinching spoiling the action.
The scoring judges judged it 96-94 to the winner, with the final judge a 95-95.
"It wasn't my greatest display but what defines champions? They succeed," the victor said in the arena as he was greeted with boos from the audience.
The Londoner got back to winning after his initial pro loss - an memorable fight with his previous opponent in February - to earn a twentieth professional win.
Various analysts felt the challenger, 31, deserved the decision but the Derbyshire fighter endured the second loss of his 28-fight professional journey.
Buatsi Claims Triumph in Dull Encounter
The fighter's advancement has stalled in recent years through promotional disputes and long spells of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now finds himself trying to achieve expectations - possibly in what seems like a final roll of the dice - under fresh management.
He started carefully, with the two boxers prepared to overcommit in a calculated opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after suffering a hand injury in the contest, was competing in only his second bout at the higher weight class.
By the fight's midpoint, Parker had kept it close, making life awkward for the favorite, who operated with a solid defense to edge the better rounds.
The crowd's patience decreased amid frequent holding, with the challenger going down various instances during grappling.
The underdog closed well, but many rounds were hard to judge. Nevertheless, ex-champion Carl Frampton - commentating on the broadcast network - had it strongly leaning for Parker, giving Buatsi just only one stanza.
The victor advances, but with the likes of hard hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still seems difficult.
Hatton Memorial Inspires All-Manchester Contest
In the co-main event, Arthur overcame Rea by split-decision in a outstanding local rivalry fight to win the European light heavyweight title.
The arena grew hushed for a deeply poignant homage ahead of the contest as ten bells tolled in honor of the city's native Hatton, who died at age 46 in September.
It was the first major televised fight night in the urban center since Hatton's death. As the concluding sound ended, the stillness transitioned to a roar of "there's just one Hatton".
The action during the bout equaled the emotion. The eventual winner was sent to the canvas by a powerful punch directly to the face in the early round, standing uncertainly to his feet on the eight count.
But the traditional red equipment of the fighter soon advanced again. On the opposite side, Rea - in rival City blue - was damaged early, noticeable damage appearing under his orbital area as the duo exchanged powerful shots.
Rea, 27, delivered effective strikes but Arthur, 34, matched the intensity with powerful upward punches as the action seldom decreased over 12 rounds.
The victor narrowly won the result with scoring tallies of draw, 115-113 and wider gap, but each competitor were persistent and full of heart, all the qualities their inspiration Hatton represented.
