UK light-heavyweight Buatsi secured a victory yet unimpressive debut to his career under recent management with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a tight ten-round contest at the Co-op Live Arena.
But the challenger found success, landing some telling clean blows in a contest where the styles didn't complement each other, with excessive holding marring the action.
The scoring judges scored it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my finest showing but what defines champions? They succeed," Buatsi stated in the arena as he was met by boos from the audience.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with Callum Smith in February - to earn a 20th pro success.
Various analysts thought the challenger, 31, deserved the win but the British boxer endured the second setback of his 28-fight professional journey.
Buatsi Secures Triumph in Uneventful Encounter
His career development has stalled in recent years through management issues and considerable time of inactivity.
Earlier forecast as the rising talent of UK boxing, he now finds himself trying to fulfil that early promise - perhaps in what feels like a ultimate opportunity - under recent support.
He started carefully, with neither fighter ready to take risks in a cagey early stages.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in 2022 after damaging his hand in the contest, was making just his second appearance at the higher weight class.
By the fight's midpoint, the underdog had stayed in contention, causing problems for Buatsi, who worked behind a tight guard to edge the cleaner stanzas.
The audience's tolerance decreased amid frequent holding, with Parker falling to the floor several times during clinches.
The underdog ended stronger, but many rounds were challenging to assess. Although, ex-champion Carl Frampton - working with Dazn - had it strongly leaning for the challenger, awarding Buatsi just one round.
Buatsi advances, but with the likes of power puncher Benavidez, and Russian star Dmitry Bivol ruling the division, the road to world glory - judging by this showing - still looks steep.
Hatton Memorial Motivates Manchester Derby Fight
In the secondary fight, Lyndon Arthur beat Rea by divided decision in a excellent local rivalry fight to secure the European light heavyweight championship.
The arena became quiet for a profoundly moving tribute before the fight as 10 bells rang in honor of local hero Ricky Hatton, who passed away at age 46 in recently.
It was the first major televised fight night in the urban center since Hatton's death. As the concluding sound disappeared, the silence became a chant of "there's only one Ricky Hatton".
The action within the ring equaled the emotion. The eventual winner was sent to the canvas by a powerful punch flush on the jaw in the second round, standing uncertainly to his feet on the count of eight.
But the red-colored shorts of Arthur soon pressed ahead again. Across the ring, Rea - in competitive blue - was damaged early, noticeable damage forming under his face as the duo exchanged hard punches.
Rea, 27, delivered effective strikes but Arthur, 34, responded in kind with powerful upward punches as the action seldom decreased over 12 rounds.
The victor edged the decision with scoring tallies of even score, close margin and 115-112, but the two athletes were relentless and full of heart, all the qualities their inspiration Hatton embodied.
