British light heavyweight Buatsi secured a victory yet disappointing beginning to his career under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a close 10-round fight at the boxing arena.
But the challenger found success, delivering effective clean blows in a match where the styles never quite clicked, with excessive holding spoiling the fight.
The scoring judges judged it 96-94 to the winner, with the third a 95-95 draw.
"It wasn't my best performance but what do champions do? They win," Buatsi commented in the arena as he was greeted with disapproval from the spectators.
The Londoner got back to winning after his initial pro loss - an epic battle with his previous opponent in February - to claim a 20th career victory.
Various analysts thought the challenger, 31, merited the decision but the contender suffered the second setback of his 28-fight professional journey.
Buatsi Claims Triumph in Dull Match
The fighter's advancement has stalled in the past few years through contract problems and long spells of inactivity.
Once tipped as the rising talent of British boxing, he now finds himself trying to achieve expectations - possibly in what appears to be a last chance - under fresh management.
He opened tentatively, with the two boxers willing to overcommit in a tentative initial rounds.
Parker, whose only previous defeat came at super-middleweight against his former opponent in two years ago after damaging his hand in the contest, was making just his second bout at the higher weight class.
By the middle rounds, Parker had made it competitive, making life awkward for Buatsi, who utilized a tight guard to edge the cleaner stanzas.
The crowd's patience diminished amid regular grabbing, with Parker going down various instances during close exchanges.
Parker closed well, but many rounds were challenging to assess. Although, former world champion Carl Frampton - working with Dazn - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
Buatsi progresses, but with the caliber of hard hitter David Benavidez, and Russian star Bivol dominating the weight class, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Memorial Fuels Manchester Derby Fight
In the co-main event, Arthur overcame Rea by close verdict in a excellent Manchester vs Manchester contest to secure the continental championship.
The arena became quiet for a profoundly moving tribute ahead of the contest as ten bells rang in honor of the city's native Ricky Hatton, who succumbed aged 46 in recently.
It was the premier televised fight night in the urban center since the passing of Hatton. As the final chime disappeared, the stillness gave way to a shout of "there's just one Ricky Hatton".
The fighting during the bout equaled the emotion. The eventual winner was knocked down by a powerful punch directly to the chin in the early round, rising shakily to his feet on the referee's count.
But the Manchester United-red attire of Arthur soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was marked up quickly, noticeable damage forming under his eye as the fighters landed punishing blows.
Rea, 27, connected with strong blows but the champion, thirty-four, responded in kind with powerful upward punches as the action rarely dropped over 12 rounds.
Arthur narrowly won the decision with official scores of 114-114, 115-113 and wider gap, but each competitor were determined and full of heart, exactly what their hero Hatton stood for.
