UK light-heavyweight Buatsi earned a win yet unimpressive start to his career under recent management with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a close ten-round bout at the Manchester venue.
But the challenger found success, connecting with powerful individual punches in a fight where the techniques didn't complement each other, with excessive holding disrupting the fight.
Two judges judged it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my finest display but what defines champions? They win," the victor commented in the ringside as he was faced disapproval from the audience.
The British fighter got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to earn a 20th pro success.
Various analysts thought the challenger, thirty-one, should have been awarded the decision but the contender suffered the second loss of his 28-match career.
The Champion Claims Triumph in Uneventful Match
Buatsi's progress has plateaued in recent years through contract problems and long spells of lack of fights.
Previously predicted as the next star of UK boxing, he now stands trying to fulfil that early promise - maybe in what appears to be a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter willing to take risks in a calculated opening few rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in two years ago after breaking his hand during the bout, was competing in only his second fight at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, causing problems for the favorite, who worked behind a tight guard to barely take the more effective rounds.
The spectators' acceptance wore thin amid constant clinching, with Parker going down multiple occasions during close exchanges.
Parker ended stronger, but multiple periods were challenging to assess. However, previous titleholder the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, giving Buatsi just one round.
Buatsi advances, but with the caliber of power puncher David Benavidez, and Russian champion Bivol leading the category, the path to championship success - on this evidence - still seems difficult.
Ricky Hatton Memorial Fuels Local Rivalry Contest
In the secondary fight, Lyndon Arthur defeated Rea by close verdict in a outstanding Manchester vs Manchester battle to secure the European light-heavyweight belt.
The arena grew hushed for a extremely emotional homage prior to the bout as ten bells rang in honor of local hero Hatton, who passed away at age 46 in September.
It was the first major televised match card in the urban center since Hatton's death. As the concluding sound faded, the quiet gave way to a shout of "there's just one Ricky Hatton".
The fighting inside the ropes reflected the sentiment. The eventual winner was floored by a significant blow squarely on the chin in the initial stage, standing uncertainly to his position on the count of eight.
But the red-colored attire of Arthur soon pressed ahead again. From the other corner, Rea - in competitive blue - was damaged quickly, heavy swelling developing under his face as the pair traded powerful shots.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, matched the intensity with stinging uppercuts as the action rarely dropped over 12 rounds.
Arthur edged the verdict with official scores of even score, close margin and wider gap, but both fighters were persistent and courageous, all the qualities their inspiration the legend embodied.
