British light heavyweight Buatsi earned a win yet unimpressive debut to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a competitive ten-round fight at the boxing arena.
But the challenger found success, delivering effective individual punches in a fight where the approaches didn't complement each other, with frequent clinching disrupting the contest.
The scoring judges had it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my best display but how do champions respond? They succeed," Buatsi commented in the arena as he was faced boos from the crowd.
The Londoner bounced back after his initial pro loss - an memorable fight with his previous opponent in last winter - to claim a 20th career victory.
Some ringside observers believed the challenger, 31, merited the victory but the Derbyshire fighter endured the second setback of his 28-fight professional journey.
Buatsi Earns Win in Dull Match
The fighter's advancement has stalled in the past few years through contract problems and extended periods of inactivity.
Earlier forecast as the future of UK boxing, he now finds himself trying to achieve expectations - perhaps in what appears to be a final roll of the dice - under fresh management.
He opened tentatively, with both competitors willing to overcommit in a cagey initial rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in 2022 after suffering a hand injury mid-fight, was competing in only his second bout at light-heavyweight.
By the middle rounds, Parker had stayed in contention, making life awkward for the favorite, who operated with a tight guard to edge the more effective stanzas.
The crowd's patience decreased amid frequent holding, with the challenger slipping to the canvas several times during close exchanges.
The underdog ended stronger, but several stanzas were challenging to assess. Although, former world champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for Parker, giving Buatsi just one round.
The victor moves on, but with the caliber of hard hitter Benavidez, and Russian champion Bivol ruling the division, the road to world glory - on this evidence - still looks steep.
Hatton Tribute Inspires All-Manchester Contest
In the secondary fight, Lyndon Arthur overcame Rea by divided decision in a excellent all-Manchester battle to win the continental belt.
The venue fell silent for a profoundly moving memorial ahead of the contest as a bell ceremony sounded in honor of Manchester's own Ricky Hatton, who died aged 46 in recently.
It was the initial significant broadcast boxing event in the city since Hatton's death. As the final chime ended, the stillness became a roar of "there's only one Hatton".
The competition during the bout equaled the emotion. Arthur was sent to the canvas by a powerful punch squarely on the jaw in the initial stage, rising shakily to his footing on the count of eight.
But the Manchester United-red shorts of the fighter soon pressed ahead again. On the opposite side, Rea - in competitive blue - was marked up soon, significant bruising appearing under his eye as the fighters landed powerful shots.
The challenger, 27, landed power punches but the champion, thirty-four, responded in kind with effective uppercuts as the intensity rarely dropped over twelve rounds.
The victor edged the decision with judges scorecards of even score, narrow lead and clearer margin, but both fighters were determined and brave, all the qualities their hero the legend represented.
