British light-heavyweight Buatsi earned a win yet unimpressive debut to life under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate appeared to earn him a majority decision in a close 10-round bout at the Co-op Live Arena.
But Parker found success, connecting with powerful clean blows in a contest where the styles failed to mesh, with constant grabbing marring the contest.
The officials scored it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my finest performance but what defines champions? They succeed," the victor commented in the ringside as he was faced disapproval from the crowd.
The British fighter got back to winning after his initial pro loss - an epic battle with Callum Smith in February - to secure a twentieth professional win.
Several boxing experts believed Parker, 31, merited the decision but the contender endured the second loss of his 28-fight career.
Buatsi Earns Win in Slow Match
The fighter's advancement has slowed in recent years through management issues and long spells of lack of fights.
Previously predicted as the future of British boxing, he now stands trying to realize his potential - possibly in what feels like a final roll of the dice - under new promotional backing.
He started carefully, with neither fighter willing to overcommit in a tentative initial rounds.
Parker, whose single earlier setback came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was making just his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for Buatsi, who worked behind a protective stance to edge the cleaner rounds.
The spectators' acceptance diminished amid frequent holding, with the challenger falling to the floor several times during close exchanges.
Parker closed well, but multiple periods were hard to judge. Although, previous titleholder the boxing analyst - working with Dazn - had it particularly wide for Parker, awarding Buatsi just only one stanza.
The victor progresses, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - on this evidence - still looks steep.
Ricky Hatton Homage Inspires Local Rivalry Contest
In the supporting bout, Arthur defeated Rea by divided decision in a excellent local rivalry battle to capture the European light heavyweight championship.
The stadium grew hushed for a deeply poignant tribute ahead of the contest as a bell ceremony tolled in remembrance of local hero Hatton, who succumbed aged 46 in September.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the final chime ended, the silence gave way to a chant of "there's only one Hatton".
The action within the ring reflected the feeling. The eventual winner was knocked down by a significant blow squarely on the face in the second round, getting up unsteadily to his footing on the eight count.
But the Manchester United-red shorts of the fighter soon pressed ahead again. From the other corner, the opponent - in rival City blue - was marked up early, noticeable damage appearing under his eye as the fighters exchanged hard punches.
Rea, 27, landed power punches but the champion, 34, responded in kind with stinging uppercuts as the intensity seldom decreased over twelve rounds.
The victor narrowly won the decision with official scores of draw, 115-113 and clearer margin, but each competitor were relentless and brave, everything their inspiration the legend stood for.
