British light-heavyweight Buatsi secured a victory yet underwhelming beginning to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a judges' verdict in a competitive 10-round contest at the boxing arena.
But Parker had his moments, delivering effective clean blows in a match where the styles never quite clicked, with constant grabbing disrupting the action.
The scoring judges judged it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my best display but how do champions respond? They succeed," Buatsi commented in the arena as he was faced negative reactions from the audience.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in February - to earn a 20th career victory.
Various analysts felt the challenger, thirty-one, should have been awarded the decision but the contender suffered the second loss of his 28-fight professional journey.
The Champion Claims Victory in Dull Match
The fighter's advancement has stalled in recent times through management issues and long spells of lack of fights.
Once tipped as the future of UK boxing, he now is positioned trying to realize his potential - maybe in what appears to be a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter willing to overcommit in a tentative opening few rounds.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago after breaking his hand mid-fight, was participating in his second bout at light-heavyweight.
By the halfway stage, Parker had kept it close, making life awkward for Buatsi, who operated with a solid defense to narrowly win the more effective periods.
The crowd's patience decreased during regular grabbing, with Parker going down several times during clinches.
The underdog ended stronger, but many rounds were hard to judge. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it significantly in favor for Parker, giving Buatsi just one round.
Buatsi progresses, but with the likes of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - judging by this showing - still seems difficult.
Hatton Memorial Inspires All-Manchester Contest
In the secondary fight, Lyndon Arthur defeated Rea by split-decision in a excellent all-Manchester battle to win the European light heavyweight belt.
The stadium became quiet for a extremely emotional tribute prior to the bout as a bell ceremony sounded in honor of Manchester's own Ricky Hatton, who passed away at age 46 in September.
It was the initial significant broadcast boxing event in the city since Hatton's death. As the final chime ended, the quiet gave way to a roar of "there's only one Hatton".
The competition inside the ropes matched the feeling. The eventual winner was sent to the canvas by a powerful punch squarely on the jaw in the initial stage, getting up unsteadily to his position on the count of eight.
But the red-colored equipment of the fighter soon came forward again. On the opposite side, the opponent - in competitive blue - was injured quickly, heavy swelling developing under his eye as the pair landed hard punches.
The challenger, 27, landed power punches but the champion, thirty-four, fought fire with fire with effective uppercuts as the intensity rarely dropped over the full distance.
Arthur narrowly won the decision with scoring tallies of 114-114, close margin and clearer margin, but both fighters were relentless and courageous, everything their hero Hatton embodied.
