British light heavyweight Buatsi secured a victory yet disappointing start to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a tight 10-round bout at the Co-op Live Arena.
But Parker landed significant shots, delivering effective clean blows in a fight where the techniques never quite clicked, with constant grabbing spoiling the action.
The scoring judges had it 96-94 to the winner, with the third a even score.
"It wasn't my greatest display but what do champions do? They prevail," the victor said in the ringside as he was faced disapproval from the crowd.
The British fighter got back to winning after his maiden career setback - an thrilling contest with his previous opponent in February - to secure a 20th career victory.
Some ringside observers felt the challenger, 31, deserved the decision but the contender endured the second defeat of his 28-fight professional journey.
Buatsi Claims Triumph in Slow Match
His career development has stalled in recent years through management issues and considerable time of inactivity.
Previously predicted as the future of the British fight scene, he now is positioned trying to realize his potential - maybe in what feels like a final roll of the dice - under fresh management.
He opened tentatively, with the two boxers willing to overcommit in a cagey opening few rounds.
Parker, whose single earlier setback came at super-middleweight against John Ryder in two years ago after breaking his hand mid-fight, was participating in his second bout at light heavyweight.
By the middle rounds, the underdog had stayed in contention, creating difficulties for Buatsi, who operated with a protective stance to edge the cleaner rounds.
The spectators' acceptance diminished during regular grabbing, with the challenger falling to the floor various instances during grappling.
The underdog ended stronger, but multiple periods were challenging to assess. However, ex-champion Carl Frampton - commentating on Dazn - had it particularly wide for the challenger, awarding Buatsi just one round.
The victor moves on, but with the likes of power puncher Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still looks steep.
Hatton Homage Fuels All-Manchester Fight
In the secondary fight, Arthur beat Rea by close verdict in a terrific all-Manchester battle to secure the European light-heavyweight championship.
The venue fell silent for a deeply poignant tribute prior to the bout as ten bells tolled in honor of the city's native Ricky Hatton, who succumbed 46 years old in recently.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the last bell faded, the stillness transitioned to a shout of "only one Hatton".
The action inside the ropes equaled the sentiment. The eventual winner was floored by a left hook directly to the jaw in the initial stage, standing uncertainly to his position on the referee's count.
But the red-colored attire of Arthur soon came forward again. On the opposite side, Rea - in competitive blue - was marked up early, heavy swelling appearing under his face as the pair landed hard punches.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, responded in kind with effective uppercuts as the intensity rarely dropped over 12 rounds.
Arthur edged the verdict with judges scorecards of even score, narrow lead and clearer margin, but both fighters were persistent and brave, everything their inspiration Hatton represented.
