UK light heavyweight Buatsi earned a win yet unimpressive beginning to life under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a split decision in a tight ten-round contest at the Manchester venue.
But the challenger had his moments, delivering effective individual punches in a match where the techniques failed to mesh, with constant grabbing marring the fight.
The scoring judges had it 96-94 in favor to Buatsi, with the remaining official a even score.
"It wasn't my greatest showing but how do champions respond? They prevail," Buatsi said in the ring as he was met by negative reactions from the spectators.
The British fighter got back to winning after his first professional defeat - an thrilling contest with his previous opponent in last winter - to claim a 20th career victory.
Some ringside observers felt the challenger, 31, merited the victory but the contender experienced the second defeat of his 28-bout professional journey.
The Champion Secures Victory in Dull Encounter
Buatsi's progress has slowed in recent years through management issues and extended periods of inactivity.
Earlier forecast as the future of UK boxing, he now stands trying to realize his potential - possibly in what seems like a final roll of the dice - under recent support.
He opened tentatively, with both competitors prepared to be aggressive in a tentative initial rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand in the contest, was competing in only his second bout at light-heavyweight.
By the middle rounds, Parker had stayed in contention, making life awkward for the favorite, who utilized a tight guard to barely take the cleaner stanzas.
The spectators' acceptance diminished because of constant clinching, with the challenger falling to the floor several times during grappling.
The underdog ended stronger, but multiple periods were difficult to score. However, previous titleholder Carl Frampton - working with Dazn - had it significantly in favor for the challenger, scoring for Buatsi just a single round.
The victor progresses, but with the likes of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Homage Motivates All-Manchester Battle
In the supporting bout, Lyndon Arthur overcame Bradley Rea by close verdict in a terrific Manchester vs Manchester fight to secure the continental belt.
The stadium grew hushed for a deeply poignant tribute ahead of the contest as ten bells rang in remembrance of the city's native Ricky Hatton, who died aged 46 in recently.
It was the first major televised match card in the city since Hatton's death. As the final chime disappeared, the silence gave way to a shout of "there's only one Hatton".
The competition during the bout equaled the sentiment. Arthur was floored by a significant blow flush on the jaw in the initial stage, rising shakily to his feet on the eight count.
But the traditional red shorts of the fighter soon advanced again. From the other corner, Rea - in competitive blue - was damaged quickly, noticeable damage appearing under his orbital area as the pair landed powerful shots.
Rea, 27, connected with strong blows but Arthur, 34, fought fire with fire with stinging uppercuts as the pace hardly diminished over 12 rounds.
The victor narrowly won the result with judges scorecards of draw, close margin and 115-112, but both fighters were relentless and brave, all the qualities their hero Hatton represented.
