UK light heavyweight Buatsi secured a victory yet disappointing debut to his career under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a majority decision in a competitive ten-round fight at the Co-op Live Arena.
But Parker landed significant shots, delivering effective individual punches in a contest where the techniques failed to mesh, with frequent clinching disrupting the action.
Two judges had it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my best showing but what do champions do? They prevail," the victor said in the ringside as he was greeted with boos from the crowd.
The Londoner got back to winning after his first professional defeat - an epic battle with his previous opponent in February - to claim a 20th career victory.
Several boxing experts believed the challenger, 31, merited the win but the contender endured the second defeat of his 28-match career.
The Champion Claims Victory in Dull Encounter
The fighter's advancement has stalled in recent years through management issues and extended periods of lack of fights.
Earlier forecast as the future of UK boxing, he now is positioned trying to achieve expectations - possibly in what seems like a ultimate opportunity - under new promotional backing.
He opened tentatively, with neither fighter willing to be aggressive in a tentative early stages.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after breaking his hand during the bout, was participating in his second bout at light-heavyweight.
By the middle rounds, Parker had made it competitive, causing problems for Buatsi, who operated with a solid defense to narrowly win the more effective rounds.
The audience's tolerance wore thin during constant clinching, with the challenger falling to the floor various instances during close exchanges.
Parker finished the stronger, but several stanzas were challenging to assess. Although, previous titleholder the boxing analyst - commentating on Dazn - had it particularly wide for Parker, awarding Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter David Benavidez, and Russian star Bivol ruling the division, the path to championship success - judging by this showing - still looks steep.
Hatton Memorial Fuels All-Manchester Battle
In the co-main event, Arthur defeated Rea by split-decision in a excellent local rivalry contest to capture the European light heavyweight title.
The stadium grew hushed for a deeply poignant homage prior to the bout as ten bells sounded in remembrance of the city's native Hatton, who died 46 years old in September.
It was the premier televised match card in the location since Hatton's passing. As the last bell disappeared, the silence gave way to a shout of "only one Hatton".
The competition during the bout reflected the feeling. Arthur was knocked down by a left hook squarely on the chin in the initial stage, standing uncertainly to his footing on the eight count.
But the red-colored equipment of the fighter soon pressed ahead again. On the opposite side, Rea - in opposing blue - was marked up early, noticeable damage forming under his face as the duo landed powerful shots.
Rea, 27, delivered effective strikes but the champion, thirty-four, matched the intensity with powerful upward punches as the intensity rarely dropped over 12 rounds.
The victor edged the verdict with judges scorecards of 114-114, narrow lead and wider gap, but each competitor were determined and full of heart, exactly what their hero Hatton stood for.
