British light heavyweight Buatsi earned a win yet disappointing debut to his career under new promoters with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a split decision in a tight ten-round bout at the Co-op Live Arena.
But the challenger found success, landing some telling single shots in a match where the techniques never quite clicked, with excessive holding spoiling the action.
The scoring judges had it 96-94 to Buatsi, with the remaining official a even score.
"It wasn't my greatest showing but what do champions do? They win," Buatsi stated in the ring as he was greeted with boos from the crowd.
The British fighter bounced back after his initial pro loss - an memorable fight with Callum Smith in last winter - to claim a twentieth professional win.
Some ringside observers believed Parker, thirty-one, merited the decision but the Derbyshire fighter experienced the second defeat of his 28-fight career.
Buatsi Secures Win in Uneventful Match
His career development has slowed in recent years through contract problems and long spells of inactivity.
Previously predicted as the rising talent of British boxing, he now finds himself trying to achieve expectations - possibly in what feels like a last chance - under fresh management.
He opened tentatively, with both competitors ready to overcommit in a cagey initial rounds.
Parker, whose only previous defeat came at super-middleweight against John Ryder in two years ago after damaging his hand mid-fight, was participating in his second fight at light-heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who worked behind a protective stance to barely take the more effective periods.
The spectators' acceptance decreased because of frequent holding, with Parker falling to the floor various instances during clinches.
The underdog finished the stronger, but many rounds were hard to judge. However, ex-champion Carl Frampton - working with Dazn - had it significantly in favor for the challenger, scoring for Buatsi just a single round.
The victor advances, but with the likes of power puncher David Benavidez, and Russian star Bivol ruling the division, the road to world glory - based on this performance - still looks steep.
Hatton Tribute Motivates Local Rivalry Battle
In the co-main event, Lyndon Arthur beat Rea by close verdict in a outstanding Manchester vs Manchester fight to secure the European light heavyweight title.
The arena grew hushed for a profoundly moving memorial ahead of the contest as ten bells tolled in memory of local hero Ricky Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the concluding sound disappeared, the stillness gave way to a roar of "only one Ricky Hatton".
The action during the bout matched the emotion. The eventual winner was floored by a powerful punch squarely on the face in the early round, standing uncertainly to his footing on the count of eight.
But the Manchester United-red equipment of the fighter soon pressed ahead again. Across the ring, the opponent - in competitive blue - was injured quickly, noticeable damage appearing under his eye as the pair landed hard punches.
Rea, 27, delivered effective strikes but the champion, thirty-four, matched the intensity with powerful upward punches as the intensity hardly diminished over twelve rounds.
Arthur narrowly won the decision with scoring tallies of draw, close margin and wider gap, but the two athletes were determined and full of heart, everything their idol the legend represented.
