UK light-heavyweight Buatsi secured a victory yet disappointing beginning to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a close ten-round contest at the boxing arena.
But Parker landed significant shots, connecting with powerful clean blows in a fight where the approaches failed to mesh, with constant grabbing marring the fight.
The scoring judges scored it 96-94 for to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest display but what do champions do? They succeed," Buatsi said in the ring as he was faced boos from the audience.
The Londoner got back to winning after his first professional defeat - an memorable fight with Callum Smith in last winter - to claim a twentieth professional win.
Various analysts thought the challenger, thirty-one, should have been awarded the decision but the Derbyshire fighter experienced the second setback of his 28-bout career.
The Champion Claims Victory in Dull Encounter
Buatsi's progress has plateaued in the past few years through promotional disputes and considerable time of inactivity.
Once tipped as the future of British boxing, he now stands trying to achieve expectations - maybe in what seems like a last chance - under fresh management.
He started carefully, with neither fighter prepared to be aggressive in a cagey opening few rounds.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second bout at the higher weight class.
By the middle rounds, Parker had stayed in contention, causing problems for Buatsi, who operated with a solid defense to barely take the cleaner stanzas.
The spectators' acceptance diminished amid regular grabbing, with the challenger falling to the floor multiple occasions during grappling.
Parker ended stronger, but many rounds were challenging to assess. Although, previous titleholder the boxing analyst - commentating on Dazn - had it significantly in favor for the challenger, awarding Buatsi just one round.
The victor advances, but with the caliber of power puncher Benavidez, and Russian champion Bivol ruling the division, the path to championship success - judging by this showing - still looks steep.
Hatton Tribute Motivates Local Rivalry Battle
In the co-main event, Lyndon Arthur defeated Bradley Rea by split-decision in a terrific Manchester vs Manchester fight to secure the European light heavyweight championship.
The arena became quiet for a deeply poignant memorial ahead of the contest as a bell ceremony rang in remembrance of the city's native Hatton, who passed away 46 years old in last month.
It was the first major televised match card in the city since Hatton's passing. As the last bell ended, the quiet became a shout of "there's only one Hatton".
The competition during the bout equaled the feeling. The eventual winner was knocked down by a powerful punch squarely on the face in the initial stage, rising shakily to his footing on the referee's count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was injured quickly, heavy swelling appearing under his face as the pair exchanged hard punches.
Rea, 27, delivered effective strikes but Arthur, 34, matched the intensity with stinging uppercuts as the pace seldom decreased over 12 rounds.
The victor narrowly won the verdict with scoring tallies of 114-114, narrow lead and 115-112, but the two athletes were determined and brave, exactly what their hero Hatton represented.
