UK light heavyweight Buatsi earned a win yet unimpressive debut to life under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a judges' verdict in a competitive ten-round fight at the boxing arena.
But Parker found success, connecting with powerful clean blows in a contest where the techniques didn't complement each other, with constant grabbing marring the action.
Two judges had it 96-94 in favor to Buatsi, with the third a 95-95.
"It wasn't my greatest display but what do champions do? They win," the victor commented in the ring as he was met by disapproval from the crowd.
The Londoner bounced back after his first professional defeat - an memorable fight with Callum Smith in last winter - to earn a 20th career victory.
Various analysts believed the challenger, 31, should have been awarded the decision but the British boxer endured the second loss of his 28-match professional journey.
Buatsi Secures Win in Slow Affair
Buatsi's progress has stalled in recent years through promotional disputes and considerable time of inactivity.
Once tipped as the future of UK boxing, he now finds himself trying to achieve expectations - possibly in what appears to be a final roll of the dice - under new promotional backing.
He started carefully, with neither fighter prepared to take risks in a tentative opening few rounds.
Parker, whose only previous defeat came at super-middleweight against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second fight at the higher weight class.
By the halfway stage, the underdog had stayed in contention, making life awkward for Buatsi, who worked behind a solid defense to edge the more effective rounds.
The crowd's patience diminished because of constant clinching, with the challenger falling to the floor multiple occasions during grappling.
Parker closed well, but several stanzas were difficult to score. Although, ex-champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just one round.
Buatsi progresses, but with the likes of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still looks steep.
Ricky Hatton Tribute Inspires Local Rivalry Fight
In the supporting bout, Lyndon Arthur defeated Bradley Rea by split-decision in a excellent all-Manchester fight to win the European light-heavyweight belt.
The arena fell silent for a deeply poignant homage prior to the bout as ten bells rang in honor of Manchester's own Ricky Hatton, who succumbed 46 years old in last month.
It was the first major televised match card in the urban center since Hatton's passing. As the last bell faded, the silence transitioned to a shout of "there's only one Ricky Hatton".
The action during the bout equaled the sentiment. The eventual winner was knocked down by a left hook squarely on the jaw in the second round, rising shakily to his position on the referee's count.
But the red-colored shorts of Arthur soon pressed ahead again. Across the ring, the opponent - in competitive blue - was marked up soon, heavy swelling developing under his face as the pair landed powerful shots.
The challenger, 27, connected with strong blows but the champion, 34, responded in kind with powerful upward punches as the intensity hardly diminished over twelve rounds.
The victor barely secured the decision with scoring tallies of draw, narrow lead and 115-112, but each competitor were relentless and brave, all the qualities their idol Hatton embodied.
