British light-heavyweight Buatsi earned a win yet unimpressive debut to his career under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a split decision in a tight ten-round bout at the boxing arena.
But the challenger landed significant shots, delivering effective clean blows in a fight where the techniques failed to mesh, with constant grabbing spoiling the contest.
The scoring judges had it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my greatest performance but what defines champions? They succeed," the victor commented in the ring as he was faced boos 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 secure a twentieth professional win.
Several boxing experts believed the challenger, 31, deserved the win but the contender experienced the second setback of his 28-bout career.
The Champion Claims Triumph in Slow Affair
Buatsi's progress has plateaued in the past few years through contract problems and long spells of inactivity.
Once tipped as the future of UK boxing, he now stands trying to achieve expectations - perhaps in what appears to be a final roll of the dice - under recent support.
He started carefully, with neither fighter willing to take risks in a cagey opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after breaking his hand mid-fight, was competing in only his second appearance at the higher weight class.
By the halfway stage, the underdog had stayed in contention, creating difficulties for Buatsi, who operated with a protective stance to edge the cleaner stanzas.
The spectators' acceptance wore thin during frequent holding, with Parker going down multiple occasions during close exchanges.
Parker ended stronger, but multiple periods were difficult to score. Nevertheless, ex-champion the boxing analyst - commentating on Dazn - had it strongly leaning for Parker, scoring for Buatsi just a single round.
The victor progresses, but with the likes of power puncher David Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - on this evidence - still looks steep.
Hatton Homage Inspires All-Manchester Fight
In the supporting bout, Lyndon Arthur beat Rea by split-decision in a terrific Manchester vs Manchester fight to win the European light heavyweight championship.
The venue fell silent for a extremely emotional memorial prior to the bout as ten bells tolled in memory of Manchester's own Hatton, who succumbed at age 46 in September.
It was the premier televised boxing event in the city since Hatton's passing. As the last bell disappeared, the quiet transitioned to a roar of "there's only one Ricky Hatton".
The competition during the bout reflected the sentiment. The eventual winner was floored by a powerful punch squarely on the face in the initial stage, standing uncertainly to his footing on the eight count.
But the traditional red equipment of Arthur soon pressed ahead again. Across the ring, Rea - in competitive blue - was damaged early, noticeable damage forming under his orbital area as the pair traded hard punches.
Rea, 27, delivered effective strikes but Arthur, thirty-four, responded in kind with powerful upward punches as the action hardly diminished over 12 rounds.
The victor barely secured the result with official scores of draw, close margin and clearer margin, but both fighters were determined and brave, all the qualities their inspiration Hatton embodied.
