British light-heavyweight Buatsi secured a victory yet disappointing start to life under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a majority decision in a tight 10-round bout at the boxing arena.
But the challenger had his moments, connecting with powerful single shots in a fight where the styles never quite clicked, with frequent clinching spoiling the fight.
Two judges had it 96-94 for to Buatsi, with the final judge a 95-95 draw.
"It wasn't my best performance but how do champions respond? They win," the victor stated in the arena as he was greeted with negative reactions from the spectators.
The Londoner bounced back after his maiden career setback - an memorable fight with Callum Smith in last winter - to claim a twentieth professional win.
Various analysts thought Parker, 31, should have been awarded the victory but the Derbyshire fighter endured the second loss of his 28-fight career.
The Champion Earns Triumph in Uneventful Match
Buatsi's progress has slowed in the past few years through promotional disputes and considerable time of inactivity.
Previously predicted as the next star of British boxing, he now finds himself trying to realize his potential - maybe in what feels like a last chance - under recent support.
He began cautiously, with both competitors willing to be aggressive in a tentative initial rounds.
Parker, whose only previous defeat came at super middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was competing in only his second appearance at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for Buatsi, who worked behind a protective stance to narrowly win the more effective periods.
The crowd's patience decreased amid regular grabbing, with the challenger going down multiple occasions during grappling.
Parker closed well, but many rounds were hard to judge. Nevertheless, previous titleholder the boxing analyst - working with the broadcast network - had it significantly in favor for the challenger, giving Buatsi just a single round.
The victor advances, but with the caliber of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Memorial Inspires All-Manchester Contest
In the secondary fight, Lyndon Arthur overcame Rea by close verdict in a excellent all-Manchester fight to capture the continental championship.
The stadium fell silent for a deeply poignant memorial ahead of the contest as ten bells sounded in honor of the city's native Ricky Hatton, who succumbed aged 46 in last month.
It was the premier televised fight night in the urban center since Hatton's passing. As the final chime ended, the silence gave way to a roar of "there's only one Ricky Hatton".
The fighting during the bout equaled the emotion. Arthur was knocked down by a significant blow flush on the chin in the initial stage, rising shakily to his feet on the referee's count.
But the red-colored shorts of Arthur soon came forward again. On the opposite side, Rea - in competitive blue - was damaged early, heavy swelling developing under his orbital area as the fighters landed powerful shots.
Rea, 27, connected with strong blows but the champion, thirty-four, matched the intensity with stinging uppercuts as the intensity rarely dropped over twelve rounds.
Arthur edged the verdict with official scores of 114-114, 115-113 and clearer margin, but both fighters were relentless and courageous, exactly what their inspiration Hatton represented.
