UK light heavyweight Buatsi secured a victory yet underwhelming beginning to his career under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a split decision in a tight ten-round bout at the boxing arena.
But Parker had his moments, landing some telling single shots in a match where the techniques never quite clicked, with frequent clinching marring the fight.
Two judges scored it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my finest performance but how do champions respond? They prevail," Buatsi stated in the ringside as he was met by disapproval from the spectators.
The Londoner bounced back after his initial pro loss - an epic battle with Callum Smith in last winter - to claim a twentieth professional win.
Several boxing experts thought the challenger, 31, deserved the decision but the British boxer endured the second loss of his 28-fight career.
Buatsi Claims Victory in Slow Match
The fighter's advancement has plateaued in the past few years through management issues and extended periods of inactivity.
Earlier forecast as the next star of British boxing, he now stands trying to realize his potential - possibly in what seems like a final roll of the dice - under fresh management.
He began cautiously, with the two boxers ready to take risks in a cagey opening few rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after breaking his hand in the contest, was participating in his second fight at light heavyweight.
By the middle rounds, the underdog had stayed in contention, making life awkward for Buatsi, who operated with a tight guard to barely take the cleaner rounds.
The audience's tolerance diminished because of constant clinching, with the challenger going down several times during close exchanges.
The underdog closed well, but many rounds were challenging to assess. Nevertheless, previous titleholder Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, giving Buatsi just a single round.
The victor progresses, but with the presence of power puncher Benavidez, and Russian star Bivol dominating the weight class, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Memorial Inspires Manchester Derby Contest
In the secondary fight, Lyndon Arthur beat Rea by divided decision in a terrific local rivalry battle to secure the European light-heavyweight belt.
The venue fell silent for a deeply poignant homage prior to the bout as ten bells sounded in remembrance of Manchester's own Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast match card in the location since the passing of Hatton. As the final chime disappeared, the silence became a roar of "there's only one Hatton".
The action inside the ropes matched the emotion. Arthur was knocked down by a significant blow flush on the chin in the initial stage, getting up unsteadily to his feet on the count of eight.
But the red-colored equipment of Arthur soon came forward again. From the other corner, the opponent - in competitive blue - was damaged soon, noticeable damage appearing under his orbital area as the duo landed punishing blows.
The challenger, 27, landed power punches but Arthur, 34, responded in kind with effective uppercuts as the action hardly diminished over 12 rounds.
Arthur barely secured the result with judges scorecards of draw, close margin and wider gap, but each competitor were persistent and brave, all the qualities their idol Hatton represented.
