British light-heavyweight Buatsi earned a win yet disappointing start to his career under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a judges' verdict in a tight ten-round bout at the Manchester venue.
But Parker landed significant shots, connecting with powerful single shots in a match where the styles never quite clicked, with frequent clinching marring the fight.
The scoring judges judged it 96-94 in favor to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my best performance but how do champions respond? They win," the victor commented in the ring as he was greeted with boos from the crowd.
The Londoner bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Various analysts thought the challenger, 31, deserved the win but the contender experienced the second loss of his 28-fight professional journey.
Buatsi Earns Win in Dull Match
His career development has slowed in recent times through promotional disputes and long spells of inactivity.
Once tipped as the next star of British boxing, he now stands trying to achieve expectations - perhaps in what seems like a last chance - under fresh management.
He opened tentatively, with neither fighter willing to be aggressive in a tentative initial rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in 2022 after suffering a hand injury in the contest, was making just his second bout at light-heavyweight.
By the middle rounds, Parker had kept it close, causing problems for the favorite, who operated with a protective stance to edge the cleaner periods.
The crowd's patience wore thin because of frequent holding, with Parker going down multiple occasions during clinches.
The underdog ended stronger, but multiple periods were challenging to assess. Although, ex-champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi moves on, but with the presence of heavy hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Hatton Tribute Inspires All-Manchester Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by split-decision in a outstanding local rivalry contest to win the continental belt.
The stadium fell silent for a deeply poignant homage ahead of the contest as a bell ceremony rang in remembrance of local hero Ricky Hatton, who passed away aged 46 in recently.
It was the initial significant broadcast boxing event in the urban center since Hatton's death. As the last bell disappeared, the quiet transitioned to a shout of "there's only one Ricky Hatton".
The fighting inside the ropes matched the feeling. The eventual winner was floored by a powerful punch squarely on the chin in the early round, standing uncertainly to his feet on the referee's count.
But the traditional red attire of Arthur soon came forward again. Across the ring, Rea - in rival City blue - was damaged soon, significant bruising forming under his eye as the fighters exchanged powerful shots.
The challenger, twenty-seven, landed power punches but the champion, 34, matched the intensity with stinging uppercuts as the action hardly diminished over 12 rounds.
The victor barely secured the result with official scores of even score, 115-113 and clearer margin, but the two athletes were persistent and courageous, everything their hero the legend embodied.
