UK light-heavyweight Buatsi secured a victory yet underwhelming start to his career under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a judges' verdict in a tight ten-round contest at the Manchester venue.
But Parker found success, connecting with powerful clean blows in a fight where the approaches failed to mesh, with constant grabbing marring the contest.
The officials judged it 96-94 for to the winner, with the final judge a even score.
"It wasn't my finest display but what do champions do? They succeed," Buatsi stated in the arena as he was greeted with boos from the audience.
The British fighter bounced back after his first professional defeat - an thrilling contest with Callum Smith in February - to earn a twentieth professional win.
Various analysts thought Parker, 31, deserved the win but the British boxer experienced the second loss of his 28-fight career.
The Champion Secures Triumph in Dull Match
The fighter's advancement has stalled in recent times through contract problems and considerable time of inactivity.
Once tipped as the next star of British boxing, he now stands trying to achieve expectations - maybe in what seems like a final roll of the dice - under fresh management.
He started carefully, with both competitors prepared to take risks in a cagey early stages.
Parker, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand mid-fight, was participating in his second appearance at light heavyweight.
By the halfway stage, the underdog had kept it close, causing problems for the favorite, who operated with a protective stance to narrowly win the better periods.
The crowd's patience decreased during regular grabbing, with Parker falling to the floor various instances during clinches.
Parker finished the stronger, but several stanzas were challenging to assess. However, previous titleholder Carl Frampton - providing analysis for Dazn - had it particularly wide for the challenger, giving Buatsi just a single round.
The victor moves on, but with the likes of hard hitter Benavidez, and Russian champion Dmitry Bivol ruling the division, the road to world glory - on this evidence - still seems difficult.
Hatton Tribute Inspires Local Rivalry Battle
In the secondary fight, Lyndon Arthur beat Rea by close verdict in a outstanding Manchester vs Manchester fight to capture the European light-heavyweight title.
The arena fell silent for a extremely emotional tribute ahead of the contest as a bell ceremony sounded in honor of Manchester's own Ricky Hatton, who passed away 46 years old in recently.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the final chime disappeared, the quiet transitioned to a roar of "there's just one Hatton".
The competition inside the ropes reflected the feeling. Arthur was floored by a left hook squarely on the face in the second round, rising shakily to his position on the referee's count.
But the traditional red equipment of Arthur soon came forward again. On the opposite side, the opponent - in rival City blue - was damaged early, noticeable damage forming under his face as the pair landed punishing blows.
The challenger, twenty-seven, connected with strong blows but Arthur, 34, matched the intensity with powerful upward punches as the pace hardly diminished over the full distance.
Arthur narrowly won the result with judges scorecards of even score, narrow lead and clearer margin, but the two athletes were relentless and full of heart, all the qualities their idol Hatton embodied.
