UK light heavyweight Buatsi made a winning yet disappointing debut to life under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a tight ten-round contest at the Co-op Live Arena.
But the challenger landed significant shots, connecting with powerful individual punches in a fight where the styles didn't complement each other, with constant grabbing disrupting the action.
The officials judged it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my finest showing but how do champions respond? They prevail," the victor commented in the ringside as he was met by boos from the crowd.
The British fighter returned to winning ways after his initial pro loss - an epic battle with Callum Smith in February - to secure a 20th career victory.
Various analysts thought the challenger, thirty-one, merited the win but the Derbyshire fighter endured the second defeat of his 28-match career.
The Champion Earns Win in Uneventful Affair
The fighter's advancement has plateaued in recent times through promotional disputes and long spells of inactivity.
Previously predicted as the future of British boxing, he now is positioned trying to fulfil that early promise - maybe in what seems like a final roll of the dice - under recent support.
He opened tentatively, with the two boxers prepared to overcommit in a tentative opening few rounds.
Parker, whose only previous defeat came at the lower weight class against John Ryder in 2022 after breaking his hand mid-fight, was participating in his second appearance at the higher weight class.
By the middle rounds, the underdog had stayed in contention, making life awkward for Buatsi, who worked behind a tight guard to barely take the better rounds.
The spectators' acceptance decreased because of frequent holding, with Parker going down several times during close exchanges.
Parker closed well, but several stanzas were challenging to assess. Although, previous titleholder Carl Frampton - providing analysis for Dazn - had it particularly wide for Parker, giving Buatsi just only one stanza.
Buatsi advances, but with the caliber of power puncher Benavidez, and Eastern European fighter Bivol ruling the division, the road to world glory - based on this performance - still appears challenging.
Ricky Hatton Tribute Fuels Local Rivalry Battle
In the co-main event, Arthur overcame Bradley Rea by split-decision in a terrific all-Manchester battle to win the European light heavyweight belt.
The venue grew hushed for a deeply poignant homage ahead of the contest as 10 bells tolled in remembrance of Manchester's own Ricky Hatton, who passed away 46 years old in recently.
It was the premier televised fight night in the urban center since the passing of Hatton. As the final chime ended, the quiet gave way to a shout of "there's only one Ricky Hatton".
The competition within the ring reflected the sentiment. Arthur was sent to the canvas by a left hook directly to the face in the initial stage, getting up unsteadily to his position on the referee's count.
But the traditional red shorts of Arthur soon advanced again. From the other corner, the opponent - in rival City blue - was damaged early, heavy swelling developing under his eye as the pair traded hard punches.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, responded in kind with stinging uppercuts as the pace hardly diminished over 12 rounds.
Arthur narrowly won the verdict with scoring tallies of even score, 115-113 and wider gap, but each competitor were relentless and brave, all the qualities their inspiration Hatton represented.
