British light-heavyweight Buatsi made a winning yet unimpressive start to his career under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a majority decision in a tight ten-round contest at the Manchester venue.
But Parker had his moments, connecting with powerful clean blows in a contest where the approaches never quite clicked, with constant grabbing spoiling the action.
The scoring judges had it 96-94 in favor to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest showing but what defines champions? They prevail," Buatsi commented in the ring as he was met by disapproval from the spectators.
The Londoner returned to winning ways after his maiden career setback - an epic battle with his previous opponent in February - to claim a 20th career victory.
Several boxing experts felt Parker, 31, deserved the win but the British boxer suffered the second defeat of his 28-fight professional journey.
The Champion Secures Win in Dull Affair
The fighter's advancement has stalled in recent times through contract problems and extended periods of inactivity.
Previously predicted as the future of UK boxing, he now stands trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter prepared to take risks in a calculated opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was participating in his second bout at light-heavyweight.
By the middle rounds, the underdog had kept it close, making life awkward for Buatsi, who operated with a protective stance to barely take the cleaner stanzas.
The audience's tolerance diminished because of frequent holding, with the challenger going down several times during close exchanges.
The underdog ended stronger, but multiple periods were challenging to assess. However, previous titleholder Carl Frampton - commentating on Dazn - had it particularly wide for Parker, awarding Buatsi just only one stanza.
Buatsi advances, but with the likes of heavy hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - on this evidence - still looks steep.
Hatton Homage Fuels Manchester Derby Fight
In the co-main event, Arthur overcame Bradley Rea by divided decision in a outstanding Manchester vs Manchester fight to win the European light heavyweight title.
The arena fell silent for a profoundly moving memorial before the fight as ten bells rang in memory of Manchester's own Hatton, who succumbed at age 46 in recently.
It was the initial significant broadcast fight night in the urban center since Hatton's passing. As the concluding sound disappeared, the quiet transitioned to a shout of "only one Hatton".
The action within the ring equaled the sentiment. Arthur was sent to the canvas by a significant blow directly to the face in the early round, rising shakily to his footing on the count of eight.
But the traditional red attire of Arthur soon came forward again. On the opposite side, Rea - in competitive blue - was damaged quickly, noticeable damage appearing under his orbital area as the fighters exchanged punishing blows.
Rea, twenty-seven, delivered effective strikes but the champion, 34, matched the intensity with powerful upward punches as the pace rarely dropped over twelve rounds.
Arthur barely secured the verdict with judges scorecards of 114-114, 115-113 and 115-112, but both fighters were persistent and brave, everything their inspiration Hatton embodied.
