UK light-heavyweight Buatsi made a winning yet disappointing beginning to life under recent management with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a split decision in a tight 10-round fight at the Manchester venue.
But the challenger found success, landing some telling individual punches in a fight where the techniques never quite clicked, with constant grabbing marring the fight.
The officials judged it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my greatest performance but what defines champions? They succeed," the victor stated in the ringside as he was met by disapproval from the spectators.
The Londoner bounced back after his maiden career setback - an memorable fight with Callum Smith in last winter - to secure a twentieth professional win.
Several boxing experts believed the challenger, 31, should have been awarded the victory but the British boxer experienced the second setback of his 28-fight professional journey.
Buatsi Earns Victory in Uneventful Match
Buatsi's progress has slowed in the past few years through contract problems and long spells of inactivity.
Once tipped as the rising talent of British boxing, he now is positioned trying to achieve expectations - possibly in what appears to be a final roll of the dice - under fresh management.
He began cautiously, with the two boxers willing to take risks in a calculated initial rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after suffering a hand injury during the bout, was competing in only his second fight at light-heavyweight.
By the halfway stage, the underdog had kept it close, creating difficulties for the favorite, who utilized a solid defense to edge the cleaner rounds.
The spectators' acceptance diminished during regular grabbing, with the challenger slipping to the canvas several times during close exchanges.
Parker ended stronger, but many rounds were hard to judge. However, previous titleholder the boxing analyst - working with Dazn - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi progresses, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still appears challenging.
Hatton Tribute Fuels Local Rivalry Battle
In the supporting bout, Lyndon Arthur beat Rea by split-decision in a terrific local rivalry battle to capture the continental title.
The venue became quiet for a deeply poignant memorial ahead of the contest as ten bells rang in remembrance of the city's native Ricky Hatton, who succumbed at age 46 in September.
It was the premier televised boxing event in the urban center since Hatton's death. As the final chime disappeared, the silence gave way to a roar of "there's only one Hatton".
The action inside the ropes matched the feeling. Arthur was knocked down by a left hook squarely on the face in the early round, rising shakily to his footing on the referee's count.
But the Manchester United-red shorts of the fighter soon pressed ahead again. From the other corner, the opponent - in opposing blue - was damaged early, significant bruising forming under his orbital area as the fighters landed powerful shots.
The challenger, twenty-seven, landed power punches but the champion, 34, fought fire with fire with effective uppercuts as the pace hardly diminished over 12 rounds.
The victor narrowly won the verdict with official scores of 114-114, narrow lead and clearer margin, but both fighters were determined and courageous, everything their inspiration the legend stood for.
