British light-heavyweight Buatsi made a winning yet disappointing beginning to his career under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic medal winner's punch output likely gained him a judges' verdict in a competitive 10-round contest at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful individual punches in a fight where the techniques failed to mesh, with constant grabbing marring the contest.
Two judges scored it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my finest display but what do champions do? They win," Buatsi stated in the ring as he was greeted with boos from the audience.
The British fighter returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in last winter - to claim a 20th pro success.
Various analysts believed Parker, 31, deserved the win but the Derbyshire fighter suffered the second defeat of his 28-bout career.
The Champion Claims Win in Slow Affair
His career development has stalled in recent years through promotional disputes and long spells of lack of fights.
Once tipped as the next star of the British fight scene, he now stands trying to realize his potential - possibly in what feels like a ultimate opportunity - under recent support.
He opened tentatively, with neither fighter willing to take risks in a calculated opening few rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after suffering a hand injury mid-fight, was competing in only his second fight at the higher weight class.
By the halfway stage, Parker had made it competitive, creating difficulties for Buatsi, who worked behind a tight guard to edge the more effective rounds.
The crowd's patience diminished during frequent holding, with Parker falling to the floor various instances during grappling.
Parker finished the stronger, but multiple periods were challenging to assess. However, ex-champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, awarding Buatsi just a single round.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian star Bivol dominating the weight class, the path to championship success - based on this performance - still appears challenging.
Hatton Memorial Inspires All-Manchester Fight
In the co-main event, Arthur overcame Rea by divided decision in a excellent local rivalry contest to win the European light-heavyweight belt.
The stadium became quiet for a profoundly moving tribute prior to the bout as a bell ceremony rang in remembrance of Manchester's own Ricky Hatton, who succumbed at age 46 in September.
It was the first major televised boxing event in the location since the passing of Hatton. As the last bell faded, the silence transitioned to a roar of "there's just one Ricky Hatton".
The action inside the ropes equaled the feeling. The eventual winner was floored by a powerful punch directly to the jaw in the second round, standing uncertainly to his footing on the referee's count.
But the Manchester United-red attire of the fighter soon advanced again. Across the ring, the opponent - in rival City blue - was damaged early, heavy swelling forming under his eye as the pair landed powerful shots.
Rea, 27, delivered effective strikes but the champion, thirty-four, fought fire with fire with stinging uppercuts as the pace rarely dropped over 12 rounds.
The victor barely secured the verdict with judges scorecards of 114-114, close margin and wider gap, but each competitor were determined and brave, everything their inspiration Hatton embodied.
