UK light heavyweight Buatsi secured a victory yet underwhelming debut to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a close 10-round contest at the Co-op Live Arena.
But Parker landed significant shots, delivering effective clean blows in a match where the approaches never quite clicked, with constant grabbing spoiling the fight.
Two judges had it 96-94 to Buatsi, with the third a even score.
"It wasn't my best showing but what do champions do? They win," the victor commented in the ringside as he was faced boos from the spectators.
The Londoner got back to winning after his first professional defeat - an epic battle with his previous opponent in February - to secure a twentieth professional win.
Some ringside observers felt the challenger, thirty-one, merited the decision but the British boxer suffered the second setback of his 28-match professional journey.
Buatsi Earns Victory in Uneventful Encounter
The fighter's advancement has plateaued in the past few years through promotional disputes and extended periods of inactivity.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to achieve expectations - possibly in what appears to be a ultimate opportunity - under fresh management.
He began cautiously, with the two boxers willing to overcommit in a calculated early stages.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago after breaking his hand in the contest, was competing in only his second fight at light heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for the favorite, who worked behind a protective stance to narrowly win the more effective periods.
The spectators' acceptance diminished amid constant clinching, with Parker slipping to the canvas multiple occasions during close exchanges.
The underdog ended stronger, but many rounds were challenging to assess. However, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it particularly wide for Parker, giving Buatsi just only one stanza.
Buatsi progresses, but with the caliber of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Tribute Fuels Local Rivalry Fight
In the secondary fight, Lyndon Arthur beat Bradley Rea by close verdict in a terrific all-Manchester battle to win the European light-heavyweight championship.
The stadium grew hushed for a extremely emotional homage before the fight as ten bells tolled in honor of local hero Hatton, who succumbed at age 46 in September.
It was the first major televised fight night in the city since Hatton's passing. As the final chime disappeared, the silence transitioned to a roar of "there's just one Hatton".
The fighting during the bout reflected the sentiment. The eventual winner was floored by a powerful punch flush on the jaw in the early round, rising shakily to his position on the referee's count.
But the Manchester United-red attire of Arthur soon came forward again. From the other corner, Rea - in rival City blue - was marked up quickly, noticeable damage developing under his eye as the pair exchanged powerful shots.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the pace rarely dropped over the full distance.
Arthur narrowly won the result with scoring tallies of draw, close margin and 115-112, but the two athletes were relentless and brave, exactly what their inspiration Hatton embodied.
