UK light heavyweight Buatsi earned a win yet underwhelming start to his career under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a competitive 10-round bout at the Manchester venue.
But Parker landed significant shots, connecting with powerful single shots in a contest where the styles failed to mesh, with constant grabbing spoiling the action.
The officials scored it 96-94 to Buatsi, with the remaining official a even score.
"It wasn't my greatest display but what defines champions? They succeed," Buatsi said in the arena as he was met by boos from the crowd.
The British fighter got back to winning after his maiden career setback - an memorable fight with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers thought Parker, thirty-one, merited the victory but the Derbyshire fighter endured the second setback of his 28-fight career.
The Champion Secures Win in Uneventful Encounter
Buatsi's progress has plateaued in recent times through contract problems and extended periods of lack of fights.
Once tipped as the rising talent of the British fight scene, he now finds himself trying to realize his potential - possibly in what appears to be a final roll of the dice - under fresh management.
He opened tentatively, with the two boxers prepared to be aggressive in a tentative initial rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was making just his second bout at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for Buatsi, who utilized a solid defense to barely take the cleaner periods.
The crowd's patience decreased because of regular grabbing, with Parker going down multiple occasions during close exchanges.
The underdog finished the stronger, but many rounds were hard to judge. Although, former world champion Carl Frampton - working with Dazn - had it significantly in favor for the challenger, scoring for Buatsi just a single round.
Buatsi advances, but with the caliber of hard hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Homage Inspires Local Rivalry Battle
In the secondary fight, Lyndon Arthur beat Rea by split-decision in a outstanding local rivalry contest to secure the European light-heavyweight championship.
The stadium grew hushed for a deeply poignant tribute prior to the bout as a bell ceremony tolled in memory of Manchester's own Hatton, who died 46 years old in last month.
It was the premier televised match card in the urban center since Hatton's death. As the final chime faded, the quiet became a shout of "there's only one Hatton".
The competition during the bout matched the feeling. Arthur was knocked down by a powerful punch directly to the jaw in the second round, standing uncertainly to his feet on the referee's count.
But the traditional red equipment of the fighter soon advanced again. On the opposite side, the opponent - in competitive blue - was injured quickly, noticeable damage appearing under his orbital area as the fighters exchanged punishing blows.
Rea, twenty-seven, landed power punches but Arthur, 34, matched the intensity with effective uppercuts as the intensity hardly diminished over twelve rounds.
The victor narrowly won the verdict with official scores of even score, close margin and 115-112, but both fighters were persistent and full of heart, exactly what their idol the legend stood for.
