UK light-heavyweight Buatsi earned a win yet disappointing beginning to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a close 10-round bout at the Manchester venue.
But Parker landed significant shots, landing some telling individual punches in a match where the techniques failed to mesh, with excessive holding disrupting the action.
Two judges scored it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest showing but how do champions respond? They prevail," Buatsi stated in the ringside as he was met by negative reactions from the crowd.
The Londoner got back to winning after his first professional defeat - an thrilling contest with Callum Smith in February - to secure a 20th pro success.
Several boxing experts believed Parker, 31, merited the victory but the contender experienced the second loss of his 28-fight career.
The Champion Secures Triumph in Uneventful Encounter
Buatsi's progress has stalled in recent years through management issues and long spells of inactivity.
Once tipped as the next star of UK boxing, he now finds himself trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under fresh management.
He began cautiously, with both competitors willing to overcommit in a calculated early stages.
Parker, whose sole prior loss came at super middleweight against his former opponent in 2022 after suffering a hand injury mid-fight, was making just his second fight at light heavyweight.
By the fight's midpoint, Parker had made it competitive, making life awkward for the favorite, who worked behind a solid defense to edge the better stanzas.
The crowd's patience wore thin amid regular grabbing, with Parker falling to the floor various instances during clinches.
The underdog closed well, but many rounds were hard to judge. Although, former world champion the boxing analyst - providing analysis for Dazn - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
The victor advances, but with the likes of power puncher Benavidez, and Russian star Bivol leading the category, the path to championship success - on this evidence - still seems difficult.
Hatton Homage Inspires Local Rivalry Fight
In the supporting bout, Lyndon Arthur overcame Rea by close verdict in a outstanding Manchester vs Manchester contest to win the continental championship.
The stadium became quiet for a deeply poignant memorial before the fight as ten bells sounded in remembrance of local hero Hatton, who died aged 46 in last month.
It was the premier televised match card in the location since the passing of Hatton. As the concluding sound disappeared, the silence became a roar of "there's just one Ricky Hatton".
The action inside the ropes matched the emotion. The eventual winner was floored by a powerful punch squarely on the chin in the second round, standing uncertainly to his feet on the eight count.
But the Manchester United-red attire of Arthur soon came forward again. Across the ring, Rea - in competitive blue - was damaged early, heavy swelling forming under his face as the duo landed hard punches.
Rea, 27, landed power punches but Arthur, thirty-four, matched the intensity with powerful upward punches as the pace hardly diminished over the full distance.
Arthur narrowly won the result with judges scorecards of draw, close margin and wider gap, but the two athletes were relentless and brave, exactly what their idol Hatton stood for.
