British light heavyweight Buatsi secured a victory yet underwhelming debut to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a judges' verdict in a close 10-round fight at the Manchester venue.
But the challenger landed significant shots, delivering effective single shots in a match where the styles failed to mesh, with frequent clinching disrupting the action.
The scoring judges had it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my best showing but what defines champions? They win," the victor commented in the ring as he was faced negative reactions from the audience.
The British fighter got back to winning after his first professional defeat - an thrilling contest with Callum Smith in February - to secure a twentieth professional win.
Several boxing experts felt Parker, thirty-one, should have been awarded the decision but the Derbyshire fighter endured the second setback of his 28-match professional journey.
The Champion Claims Win in Slow Match
The fighter's advancement has plateaued in recent times through promotional disputes and extended periods of lack of fights.
Earlier forecast as the future of British boxing, he now stands trying to fulfil that early promise - perhaps in what appears to be a last chance - under recent support.
He started carefully, with both competitors willing to overcommit in a cagey early stages.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in 2022 after suffering a hand injury in the contest, was competing in only his second appearance at the higher weight class.
By the middle rounds, Parker had made it competitive, creating difficulties for Buatsi, who worked behind a solid defense to narrowly win the cleaner periods.
The audience's tolerance decreased during regular grabbing, with Parker falling to the floor several times during close exchanges.
Parker finished the stronger, but several stanzas were difficult to score. Although, ex-champion the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the caliber of power puncher David Benavidez, and Russian star Bivol leading the category, the road to world glory - judging by this showing - still looks steep.
Hatton Homage Fuels Manchester Derby Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by close verdict in a excellent all-Manchester battle to win the European light-heavyweight championship.
The venue became quiet for a profoundly moving homage before the fight as 10 bells rang in honor of local hero Ricky Hatton, who died 46 years old in September.
It was the initial significant broadcast boxing event in the city since Hatton's death. As the concluding sound ended, the quiet gave way to a shout of "there's just one Ricky Hatton".
The competition within the ring equaled the feeling. Arthur was knocked down by a powerful punch directly to the jaw in the early round, rising shakily to his footing on the eight count.
But the Manchester United-red attire of Arthur soon came forward again. On the opposite side, Rea - in opposing blue - was damaged early, heavy swelling appearing under his face as the fighters landed hard punches.
Rea, 27, connected with strong blows but the champion, 34, fought fire with fire with effective uppercuts as the intensity hardly diminished over twelve rounds.
Arthur narrowly won the result with scoring tallies of 114-114, close margin and wider gap, but both fighters were persistent and full of heart, all the qualities their hero the legend embodied.
