UK light heavyweight Buatsi made a winning yet unimpressive beginning to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a split decision in a tight ten-round bout at the Co-op Live Arena.
But Parker had his moments, connecting with powerful clean blows in a fight where the techniques never quite clicked, with frequent clinching marring the contest.
Two judges scored it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my finest performance but what defines champions? They win," Buatsi commented in the arena as he was greeted with negative reactions from the audience.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in February - to secure a twentieth professional win.
Some ringside observers believed Parker, thirty-one, deserved the victory but the Derbyshire fighter endured the second setback of his 28-fight career.
The Champion Secures Victory in Uneventful Affair
Buatsi's progress has slowed in the past few years through contract problems and long spells of lack of fights.
Earlier forecast as the future of the British fight scene, he now is positioned trying to fulfil that early promise - maybe in what appears to be a ultimate opportunity - under recent support.
He opened tentatively, with both competitors prepared to overcommit in a cagey early stages.
Parker, whose sole prior loss came at super-middleweight against his former opponent in two years ago after breaking his hand in the contest, was participating in his second appearance at light-heavyweight.
By the middle rounds, Parker had stayed in contention, causing problems for Buatsi, who operated with a solid defense to narrowly win the cleaner stanzas.
The crowd's patience diminished because of constant clinching, with Parker going down several times during grappling.
Parker closed well, but multiple periods were challenging to assess. However, former world champion Carl Frampton - commentating on Dazn - had it particularly wide for Parker, awarding Buatsi just one round.
Buatsi advances, but with the likes of hard hitter Benavidez, and Eastern European fighter Bivol leading the category, the road to world glory - on this evidence - still looks steep.
Hatton Homage Fuels Manchester Derby Contest
In the co-main event, Lyndon Arthur overcame Rea by close verdict in a excellent Manchester vs Manchester battle to win the European light-heavyweight championship.
The venue grew hushed for a profoundly moving tribute prior to the bout as 10 bells rang in remembrance of the city's native Ricky Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast match card in the location since the passing of Hatton. As the last bell ended, the silence became a chant of "only one Ricky Hatton".
The fighting during the bout equaled the emotion. The eventual winner was knocked down by a left hook directly to the face in the second round, standing uncertainly to his feet on the eight count.
But the Manchester United-red attire of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was marked up early, heavy swelling developing under his eye as the pair exchanged powerful shots.
Rea, 27, delivered effective strikes but Arthur, thirty-four, matched the intensity with effective uppercuts as the action hardly diminished over the full distance.
Arthur narrowly won the result with official scores of even score, narrow lead and clearer margin, but each competitor were determined and full of heart, all the qualities their idol the legend stood for.
