UK light heavyweight Buatsi secured a victory yet unimpressive start to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a judges' verdict in a tight ten-round contest at the Manchester venue.
But the challenger landed significant shots, landing some telling single shots in a fight where the styles never quite clicked, with constant grabbing disrupting the fight.
The scoring judges had it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest display but what defines champions? They succeed," Buatsi said in the arena as he was faced negative reactions from the spectators.
The British fighter returned to winning ways after his maiden career setback - an memorable fight with his previous opponent in last winter - to secure a 20th pro success.
Various analysts believed Parker, thirty-one, merited the victory but the Derbyshire fighter experienced the second defeat of his 28-fight professional journey.
The Champion Claims Triumph in Dull Match
Buatsi's progress has plateaued in recent years through contract problems and considerable time of inactivity.
Once tipped as the rising talent of UK boxing, he now is positioned trying to realize his potential - perhaps in what appears to be a final roll of the dice - under fresh management.
He started carefully, with the two boxers prepared to overcommit in a tentative opening few rounds.
Parker, whose single earlier setback came at super middleweight against his former opponent in 2022 after breaking his hand mid-fight, was participating in his second fight at the higher weight class.
By the halfway stage, Parker had stayed in contention, creating difficulties for Buatsi, who utilized a tight guard to barely take the cleaner periods.
The audience's tolerance diminished because of frequent holding, with Parker slipping to the canvas multiple occasions during close exchanges.
The underdog closed well, but multiple periods were challenging to assess. Although, former world champion Carl Frampton - commentating on the broadcast network - had it strongly leaning for Parker, giving Buatsi just one round.
Buatsi advances, but with the presence of power puncher Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Tribute Inspires Manchester Derby Contest
In the secondary fight, Lyndon Arthur overcame Rea by divided decision in a outstanding local rivalry fight to secure the European light-heavyweight belt.
The arena became quiet for a profoundly moving homage prior to the bout as a bell ceremony sounded in remembrance of local hero Ricky Hatton, who succumbed at age 46 in September.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the concluding sound faded, the quiet transitioned to a shout of "there's just one Hatton".
The fighting during the bout equaled the sentiment. Arthur was floored by a significant blow directly to the jaw in the initial stage, rising shakily to his position on the eight count.
But the Manchester United-red shorts of Arthur soon came forward again. Across the ring, the opponent - in rival City blue - was damaged soon, noticeable damage appearing under his orbital area as the duo traded powerful shots.
The challenger, twenty-seven, connected with strong blows but the champion, 34, matched the intensity with stinging uppercuts as the pace rarely dropped over twelve rounds.
Arthur narrowly won the decision with judges scorecards of draw, narrow lead and wider gap, but the two athletes were determined and brave, exactly what their inspiration Hatton stood for.
