British light-heavyweight Buatsi earned a win yet disappointing debut to his career under recent management with a decision win over Zach Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a split decision in a tight ten-round bout at the Manchester venue.
But the challenger landed significant shots, connecting with powerful clean blows in a match where the styles never quite clicked, with frequent clinching disrupting the fight.
The scoring judges judged it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my best display but how do champions respond? They win," Buatsi said in the arena as he was faced disapproval from the crowd.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in last winter - to earn a twentieth professional win.
Several boxing experts thought Parker, thirty-one, should have been awarded the victory but the British boxer endured the second defeat of his 28-bout career.
The Champion Secures Win in Dull Encounter
His career development has slowed in recent times through promotional disputes and extended periods of inactivity.
Previously predicted as the next star of British boxing, he now finds himself trying to achieve expectations - perhaps in what seems like a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers prepared to take risks in a tentative initial rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in 2022 after suffering a hand injury mid-fight, was making just his second fight at light-heavyweight.
By the middle rounds, the underdog had kept it close, making life awkward for the favorite, who utilized a tight guard to narrowly win the cleaner stanzas.
The crowd's patience wore thin during constant clinching, with the challenger falling to the floor multiple occasions during grappling.
The underdog closed well, but several stanzas were challenging to assess. Although, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, giving Buatsi just a single round.
Buatsi advances, but with the presence of power puncher Benavidez, and Eastern European fighter Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Homage Motivates Manchester Derby Fight
In the supporting bout, Lyndon Arthur overcame Rea by close verdict in a excellent local rivalry fight to secure the European light heavyweight belt.
The stadium grew hushed for a extremely emotional memorial before the fight as a bell ceremony tolled in memory of Manchester's own Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the final chime ended, the stillness transitioned to a chant of "there's just one Hatton".
The competition within the ring matched the sentiment. Arthur was sent to the canvas by a left hook flush on the face in the early round, getting up unsteadily to his position on the count of eight.
But the red-colored equipment of the fighter soon pressed ahead again. Across the ring, Rea - in competitive blue - was marked up quickly, heavy swelling forming under his orbital area as the duo landed powerful shots.
The challenger, 27, connected with strong blows but Arthur, thirty-four, responded in kind with powerful upward punches as the pace rarely dropped over twelve rounds.
Arthur narrowly won the decision with judges scorecards of 114-114, close margin and 115-112, but each competitor were persistent and brave, everything their idol Hatton represented.
