British light-heavyweight Buatsi earned a win yet unimpressive start to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a majority decision in a tight 10-round fight at the boxing arena.
But the challenger had his moments, delivering effective clean blows in a contest where the approaches never quite clicked, with constant grabbing spoiling the contest.
Two judges scored it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest showing but how do champions respond? They succeed," Buatsi said in the ringside as he was greeted with disapproval from the crowd.
The Londoner got back to winning after his maiden career setback - an epic battle with his previous opponent in February - to secure a twentieth professional win.
Several boxing experts felt Parker, thirty-one, merited the victory but the contender experienced the second defeat of his 28-bout professional journey.
The Champion Earns Victory in Uneventful Match
His career development has slowed in recent years through contract problems and considerable time of lack of fights.
Earlier forecast as the rising talent of British boxing, he now stands trying to achieve expectations - perhaps in what seems like a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers prepared to be aggressive in a tentative opening few rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand mid-fight, was competing in only his second appearance at the higher weight class.
By the middle rounds, Parker had stayed in contention, creating difficulties for Buatsi, who operated with a protective stance to edge the more effective stanzas.
The spectators' acceptance diminished during regular grabbing, with Parker slipping to the canvas several times during clinches.
Parker closed well, but many rounds were challenging to assess. Nevertheless, ex-champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just a single round.
The victor advances, but with the likes of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Homage Inspires Local Rivalry Contest
In the supporting bout, Lyndon Arthur defeated Rea by close verdict in a excellent Manchester vs Manchester fight to secure the continental belt.
The arena grew hushed for a profoundly moving homage before the fight as ten bells tolled in honor of local hero Ricky Hatton, who died at age 46 in last month.
It was the first major televised boxing event in the urban center since Hatton's passing. As the last bell ended, the quiet became a chant of "there's just one Hatton".
The fighting inside the ropes equaled the emotion. Arthur was knocked down by a left hook squarely on the jaw in the second round, getting up unsteadily to his feet on the count of eight.
But the traditional red equipment of the fighter soon pressed ahead again. On the opposite side, Rea - in rival City blue - was injured early, noticeable damage developing under his eye as the pair landed hard punches.
The challenger, twenty-seven, connected with strong blows but the champion, 34, matched the intensity with stinging uppercuts as the pace hardly diminished over 12 rounds.
Arthur barely secured the result with judges scorecards of draw, close margin and 115-112, but the two athletes were persistent and full of heart, all the qualities their hero Hatton embodied.
