British light heavyweight Buatsi secured a victory yet underwhelming debut to his career under new promoters with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a close 10-round contest at the Co-op Live Arena.
But Parker had his moments, landing some telling individual punches in a contest where the techniques failed to mesh, with excessive holding disrupting the fight.
The scoring judges scored it 96-94 in favor to Buatsi, with the third a 95-95.
"It wasn't my greatest showing but how do champions respond? They succeed," Buatsi said in the ringside as he was faced disapproval from the spectators.
The Londoner got back to winning after his initial pro loss - an epic battle with Callum Smith in last winter - to claim a twentieth professional win.
Various analysts felt the challenger, thirty-one, merited the win but the British boxer experienced the second loss of his 28-match professional journey.
Buatsi Earns Win in Slow Match
The fighter's advancement has plateaued in recent years through management issues and long spells of inactivity.
Earlier forecast as the future of UK boxing, he now finds himself trying to fulfil that early promise - perhaps in what appears to be a last chance - under fresh management.
He began cautiously, with both competitors willing to overcommit in a cagey opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after damaging his hand during the bout, was making just his second bout at light heavyweight.
By the middle rounds, the underdog had made it competitive, creating difficulties for the favorite, who utilized a protective stance to barely take the cleaner stanzas.
The crowd's patience diminished during constant clinching, with Parker going down various instances during close exchanges.
Parker closed well, but multiple periods were challenging to assess. Although, former world champion Carl Frampton - commentating on Dazn - had it particularly wide for the challenger, awarding Buatsi just a single round.
Buatsi progresses, but with the caliber of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - judging by this showing - still looks steep.
Ricky Hatton Memorial Inspires Local Rivalry Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by split-decision in a outstanding Manchester vs Manchester fight to capture the European light-heavyweight championship.
The arena grew hushed for a profoundly moving memorial ahead of the contest as 10 bells sounded in remembrance of local hero Ricky Hatton, who passed away 46 years old in September.
It was the premier televised match card in the city since the passing of Hatton. As the final chime faded, the silence gave way to a roar of "there's just one Hatton".
The action during the bout reflected the emotion. The eventual winner was knocked down by a significant blow directly to the face in the second round, standing uncertainly to his position on the eight count.
But the Manchester United-red shorts of the fighter soon came forward again. From the other corner, Rea - in rival City blue - was damaged soon, heavy swelling forming under his eye as the fighters landed punishing blows.
The challenger, 27, landed power punches but Arthur, thirty-four, matched the intensity with powerful upward punches as the intensity seldom decreased over the full distance.
Arthur narrowly won the decision with scoring tallies of even score, narrow lead and 115-112, but both fighters were relentless and full of heart, exactly what their inspiration the legend embodied.
