UK light-heavyweight Buatsi earned a win yet disappointing beginning to his career under recent management with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a close 10-round contest at the Manchester venue.
But Parker found success, landing some telling clean blows in a match where the techniques didn't complement each other, with excessive holding spoiling the fight.
Two judges scored it 96-94 in favor to Buatsi, with the final judge a 95-95.
"It wasn't my best showing but how do champions respond? They win," Buatsi commented in the arena as he was faced disapproval from the spectators.
The British fighter bounced back after his maiden career setback - an memorable fight with Callum Smith in last winter - to secure a twentieth professional win.
Various analysts believed the challenger, 31, should have been awarded the victory but the contender endured the second setback of his 28-bout professional journey.
Buatsi Secures Win in Uneventful Encounter
The fighter's advancement has stalled in recent years through promotional disputes and long spells of inactivity.
Earlier forecast as the future of UK boxing, he now is positioned trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under recent support.
He opened tentatively, with both competitors willing to be aggressive in a cagey early stages.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after suffering a hand injury in the contest, was competing in only his second appearance at the higher weight class.
By the halfway stage, Parker had made it competitive, creating difficulties for the favorite, who operated with a tight guard to edge the more effective stanzas.
The audience's tolerance diminished amid frequent holding, with the challenger falling to the floor several times during close exchanges.
The underdog finished the stronger, but many rounds were hard to judge. However, previous titleholder Carl Frampton - working with Dazn - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Homage Inspires Local Rivalry Battle
In the secondary fight, Arthur overcame Bradley Rea by close verdict in a excellent local rivalry contest to secure the European light-heavyweight belt.
The venue became quiet for a deeply poignant homage before the fight as 10 bells tolled in honor of the city's native Ricky Hatton, who died aged 46 in last month.
It was the first major televised boxing event in the city since Hatton's death. As the concluding sound ended, the silence gave way to a chant of "there's only one Hatton".
The action during the bout matched the emotion. The eventual winner was floored by a significant blow squarely on the chin in the early round, standing uncertainly to his position on the referee's count.
But the traditional red shorts of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was injured early, significant bruising forming under his eye as the pair traded punishing blows.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, responded in kind with effective uppercuts as the intensity rarely dropped over twelve rounds.
Arthur barely secured the result with judges scorecards of draw, close margin and clearer margin, but each competitor were relentless and courageous, exactly what their inspiration the legend embodied.
