UK light-heavyweight Buatsi made a winning yet unimpressive beginning to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a majority decision in a competitive ten-round fight at the Manchester venue.
But the challenger had his moments, delivering effective individual punches in a match where the styles didn't complement each other, with excessive holding marring the action.
The scoring judges judged it 96-94 for to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest performance but what defines champions? They succeed," the victor said in the arena as he was faced disapproval from the crowd.
The British fighter got back to winning after his maiden career setback - an epic battle with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers thought Parker, thirty-one, merited the decision but the British boxer experienced the second defeat of his 28-bout career.
Buatsi Secures Win in Dull Affair
Buatsi's progress has plateaued in recent years through promotional disputes and considerable time of lack of fights.
Earlier forecast as the next star of British boxing, he now is positioned trying to fulfil that early promise - perhaps in what seems like a last chance - under recent support.
He started carefully, with the two boxers willing to overcommit in a cagey initial rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in two years ago after breaking his hand in the contest, was competing in only his second bout at light-heavyweight.
By the halfway stage, the underdog had kept it close, causing problems for Buatsi, who worked behind a protective stance to barely take the more effective rounds.
The spectators' acceptance diminished amid frequent holding, with the challenger falling to the floor various instances during close exchanges.
Parker finished the stronger, but multiple periods were difficult to score. Although, ex-champion the boxing analyst - working with Dazn - had it particularly wide for Parker, awarding Buatsi just one round.
Buatsi progresses, but with the likes of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still appears challenging.
Hatton Memorial Fuels All-Manchester Contest
In the co-main event, Lyndon Arthur beat Rea by divided decision in a outstanding local rivalry battle to capture the European light-heavyweight title.
The arena grew hushed for a extremely emotional tribute before the fight as 10 bells tolled in honor of local hero Ricky Hatton, who passed away 46 years old in September.
It was the premier televised boxing event in the urban center since Hatton's passing. As the final chime faded, the silence became a roar of "only one Ricky Hatton".
The fighting during the bout reflected the feeling. Arthur was sent to the canvas by a left hook flush on the chin in the early round, standing uncertainly to his position on the count of eight.
But the traditional red attire of the fighter soon came forward again. Across the ring, Rea - in rival City blue - was injured early, noticeable damage appearing under his face as the pair traded punishing blows.
Rea, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with powerful upward punches as the action seldom decreased over 12 rounds.
The victor barely secured the verdict with official scores of even score, close margin and wider gap, but the two athletes were relentless and brave, all the qualities their hero Hatton embodied.
