UK light heavyweight Buatsi earned a win yet underwhelming beginning to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a split decision in a close ten-round contest at the Manchester venue.
But the challenger landed significant shots, delivering effective individual punches in a match where the techniques never quite clicked, with constant grabbing spoiling the action.
The officials judged it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my finest showing but what defines champions? They win," Buatsi stated in the arena as he was greeted with negative reactions from the crowd.
The Londoner returned to winning ways after his first professional defeat - an epic battle with Callum Smith in February - to claim a 20th pro success.
Some ringside observers believed Parker, 31, merited the win but the contender suffered the second defeat of his 28-match career.
Buatsi Claims Win in Dull Match
The fighter's advancement has stalled in the past few years through contract problems and long spells of inactivity.
Previously predicted as the rising talent of British boxing, he now finds himself trying to fulfil that early promise - possibly in what appears to be a last chance - under new promotional backing.
He opened tentatively, with neither fighter prepared 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 suffering a hand injury in the contest, was making just his second fight at the higher weight class.
By the fight's midpoint, the underdog had stayed in contention, causing problems for Buatsi, who operated with a tight guard to edge the more effective rounds.
The audience's tolerance diminished amid constant clinching, with the challenger slipping to the canvas various instances during grappling.
Parker closed well, but many rounds were hard to judge. Although, previous titleholder Carl Frampton - working with the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the caliber of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still seems difficult.
Ricky Hatton Tribute Motivates All-Manchester Contest
In the supporting bout, Lyndon Arthur overcame Bradley Rea by divided decision in a excellent all-Manchester contest to secure the European light-heavyweight belt.
The arena grew hushed for a profoundly moving tribute ahead of the contest as 10 bells tolled in honor of local hero Ricky Hatton, who succumbed 46 years old in last month.
It was the first major televised fight night in the urban center since Hatton's death. As the last bell faded, the quiet transitioned to a shout of "there's only one Hatton".
The competition during the bout matched the sentiment. The eventual winner was sent to the canvas by a powerful punch flush on the face in the early round, standing uncertainly to his footing on the eight count.
But the red-colored equipment of the fighter soon advanced again. From the other corner, Rea - in competitive blue - was injured early, significant bruising developing under his orbital area as the pair traded hard punches.
Rea, twenty-seven, connected with strong blows but the champion, 34, fought fire with fire with stinging uppercuts as the action seldom decreased over the full distance.
Arthur narrowly won the decision with scoring tallies of even score, 115-113 and wider gap, but each competitor were determined and brave, all the qualities their inspiration the legend stood for.
