British light-heavyweight Buatsi earned a win yet disappointing debut to life under recent management with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a majority decision in a tight 10-round bout at the Manchester venue.
But the challenger had his moments, landing some telling individual punches in a match where the techniques never quite clicked, with constant grabbing disrupting the contest.
The scoring judges had it 96-94 for to the winner, with the third a 95-95.
"It wasn't my greatest showing but what defines champions? They win," the victor commented in the ring as he was met by boos from the audience.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in last winter - to secure a 20th career victory.
Several boxing experts believed Parker, 31, should have been awarded the victory but the British boxer suffered the second setback of his 28-match career.
The Champion Secures Victory in Dull Match
His career development has stalled in the past few years through management issues and long spells of inactivity.
Earlier forecast as the future of UK boxing, he now stands trying to achieve expectations - perhaps in what seems like a last chance - under new promotional backing.
He started carefully, with neither fighter willing to overcommit in a tentative opening few rounds.
Parker, whose only previous defeat came at super middleweight against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for Buatsi, who operated with a solid defense to barely take the cleaner stanzas.
The audience's tolerance decreased during frequent holding, with Parker slipping to the canvas various instances during grappling.
The underdog ended stronger, but several stanzas were difficult to score. However, previous titleholder Carl Frampton - commentating on the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
The victor advances, but with the caliber of power puncher Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still looks steep.
Ricky Hatton Memorial Inspires All-Manchester Contest
In the secondary fight, Lyndon Arthur beat Bradley Rea by divided decision in a terrific Manchester vs Manchester contest to capture the European light heavyweight title.
The arena grew hushed for a extremely emotional memorial prior to the bout as a bell ceremony rang in remembrance of local hero Ricky Hatton, who succumbed aged 46 in recently.
It was the premier televised fight night in the city since Hatton's death. As the concluding sound ended, the quiet gave way to a chant of "there's only one Ricky Hatton".
The competition during the bout matched the feeling. Arthur was sent to the canvas by a left hook directly to the jaw in the early round, getting up unsteadily to his feet on the count of eight.
But the Manchester United-red equipment of Arthur soon came forward again. From the other corner, the opponent - in competitive blue - was injured quickly, heavy swelling forming under his orbital area as the fighters traded hard punches.
Rea, twenty-seven, landed power punches but the champion, thirty-four, responded in kind with stinging uppercuts as the intensity rarely dropped over the full distance.
The victor barely secured the result with scoring tallies of draw, 115-113 and 115-112, but each competitor were determined and courageous, everything their inspiration the legend embodied.
