British light heavyweight Buatsi secured a victory yet underwhelming start to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a tight 10-round bout at the Co-op Live Arena.
But the challenger landed significant shots, connecting with powerful clean blows in a fight where the approaches never quite clicked, with excessive holding disrupting the contest.
Two judges had it 96-94 in favor to Buatsi, with the final judge a 95-95.
"It wasn't my best performance but what defines champions? They win," the victor stated in the arena as he was greeted with boos from the crowd.
The Londoner bounced back after his first professional defeat - an thrilling contest with Callum Smith in February - to secure a twentieth professional win.
Several boxing experts felt Parker, 31, deserved the victory but the Derbyshire fighter suffered the second loss of his 28-match career.
The Champion Earns Triumph in Slow Affair
Buatsi's progress has plateaued in recent times through management issues and extended periods of inactivity.
Once tipped as the future of UK boxing, he now is positioned trying to realize his potential - perhaps in what appears to be a ultimate opportunity - under new promotional backing.
He began cautiously, with the two boxers ready to overcommit in a calculated initial rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after damaging his hand mid-fight, was participating in his second appearance at light heavyweight.
By the middle rounds, the underdog had stayed in contention, causing problems for Buatsi, who utilized a protective stance to narrowly win the more effective rounds.
The spectators' acceptance decreased amid regular grabbing, with Parker going down various instances during grappling.
Parker finished the stronger, but multiple periods were difficult to score. However, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
The victor progresses, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the path to championship success - based on this performance - still seems difficult.
Hatton Memorial Motivates All-Manchester Contest
In the supporting bout, Lyndon Arthur overcame Bradley Rea by divided decision in a outstanding Manchester vs Manchester fight to secure the European light heavyweight title.
The arena became quiet for a profoundly moving homage before the fight as ten bells tolled in memory of Manchester's own Ricky Hatton, who died 46 years old in recently.
It was the initial significant broadcast boxing event in the urban center since Hatton's death. As the final chime disappeared, the stillness transitioned to a roar of "there's only one Hatton".
The competition during the bout equaled the emotion. The eventual winner was knocked down by a powerful punch directly to the jaw in the early round, getting up unsteadily to his footing on the referee's count.
But the Manchester United-red shorts of Arthur soon pressed ahead again. From the other corner, Rea - in opposing blue - was injured early, significant bruising forming under his face as the pair traded punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the action seldom decreased over 12 rounds.
Arthur narrowly won the result with official scores of 114-114, close margin and 115-112, but both fighters were persistent and courageous, everything their idol the legend embodied.
