British light heavyweight Buatsi secured a victory yet unimpressive debut to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a tight 10-round fight at the boxing arena.
But Parker found success, connecting with powerful individual punches in a match where the styles didn't complement each other, with excessive holding disrupting the fight.
The scoring judges scored it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my best showing but what do champions do? They succeed," Buatsi said in the ring as he was faced boos from the audience.
The British fighter got back to winning after his first professional defeat - an epic battle with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers thought Parker, 31, merited the decision but the Derbyshire fighter experienced the second defeat of his 28-bout professional journey.
The Champion Secures Win in Slow Affair
His career development has stalled in recent times through management issues and long spells of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now is positioned trying to realize his potential - possibly in what feels like a final roll of the dice - under fresh management.
He opened tentatively, with the two boxers ready to overcommit in a tentative opening few rounds.
Parker, whose only previous defeat came at the lower weight class against his former opponent in 2022 after damaging his hand during the bout, was making just his second fight at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, making life awkward for Buatsi, who worked behind a solid defense to barely take the better periods.
The crowd's patience diminished during constant clinching, with Parker going down multiple occasions during close exchanges.
The underdog closed well, but multiple periods were challenging to assess. However, former world champion Carl Frampton - commentating on Dazn - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
Buatsi advances, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still appears challenging.
Ricky Hatton Homage Motivates Manchester Derby Battle
In the secondary fight, Arthur overcame Rea by split-decision in a outstanding all-Manchester contest to secure the continental belt.
The arena became quiet for a deeply poignant homage ahead of the contest as a bell ceremony rang in memory of Manchester's own Ricky Hatton, who succumbed 46 years old in recently.
It was the premier televised fight night in the city since the passing of Hatton. As the final chime disappeared, the stillness transitioned to a roar of "only one Hatton".
The fighting inside the ropes matched the sentiment. The eventual winner was sent to the canvas by a significant blow flush on the chin in the initial stage, standing uncertainly to his footing on the referee's count.
But the Manchester United-red equipment of Arthur soon advanced again. Across the ring, Rea - in competitive blue - was damaged early, significant bruising developing under his orbital area as the fighters exchanged hard punches.
Rea, 27, connected with strong blows but Arthur, thirty-four, responded in kind with effective uppercuts as the action hardly diminished over 12 rounds.
The victor edged the result with official scores of 114-114, 115-113 and 115-112, but both fighters were determined and full of heart, all the qualities their hero Hatton stood for.
