UK light-heavyweight Buatsi secured a victory yet underwhelming debut to life under recent management with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a close 10-round fight at the boxing arena.
But Parker had his moments, connecting with powerful individual punches in a contest where the approaches never quite clicked, with constant grabbing marring the fight.
The scoring judges scored it 96-94 to Buatsi, with the third a even score.
"It wasn't my greatest display but what do champions do? They win," Buatsi said in the arena as he was faced boos from the audience.
The Londoner bounced back after his first professional defeat - an epic battle with Callum Smith in February - to claim a 20th career victory.
Some ringside observers thought the challenger, 31, merited the win but the contender suffered the second setback of his 28-fight career.
The Champion Earns Win in Slow Encounter
The fighter's advancement has stalled in recent years through promotional disputes and long spells of inactivity.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to achieve expectations - perhaps in what seems like a last chance - under new promotional backing.
He started carefully, with the two boxers willing to take risks in a calculated early stages.
Parker, whose only previous defeat came at the lower weight class against John Ryder in two years ago after suffering a hand injury in the contest, was making just his second fight at light heavyweight.
By the fight's midpoint, the underdog had stayed in contention, causing problems for Buatsi, who utilized a tight guard to edge the cleaner rounds.
The spectators' acceptance wore thin amid frequent holding, with the challenger slipping to the canvas various instances during grappling.
Parker ended stronger, but multiple periods were hard to judge. Although, former world champion Carl Frampton - commentating on Dazn - had it strongly leaning for Parker, scoring for Buatsi just one round.
Buatsi advances, but with the caliber of power puncher Benavidez, and Russian champion Bivol ruling the division, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Tribute Motivates Local Rivalry Fight
In the co-main event, Lyndon Arthur defeated Rea by divided decision in a outstanding all-Manchester battle to capture the European light-heavyweight belt.
The venue fell silent for a extremely emotional tribute prior to the bout as 10 bells tolled in honor of the city's native Hatton, who died at age 46 in last month.
It was the premier televised match card in the urban center since Hatton's passing. As the last bell disappeared, the stillness gave way to a shout of "only one Ricky Hatton".
The action within the ring equaled the emotion. Arthur was knocked down by a powerful punch flush on the chin in the early round, rising shakily to his position on the eight count.
But the traditional red equipment of Arthur soon pressed ahead again. From the other corner, the opponent - in opposing blue - was injured early, noticeable damage forming under his orbital area as the pair landed punishing blows.
Rea, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the action seldom decreased over the full distance.
The victor edged the decision with judges scorecards of 114-114, 115-113 and 115-112, but the two athletes were determined and courageous, exactly what their idol the legend embodied.
