British light heavyweight Buatsi made a winning yet underwhelming beginning to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a split decision in a close 10-round contest at the boxing arena.
But the challenger had his moments, landing some telling single shots in a fight where the styles failed to mesh, with frequent clinching marring the fight.
Two judges judged it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my finest showing but what do champions do? They win," Buatsi commented in the ringside as he was faced negative reactions from the crowd.
The Londoner got back to winning after his initial pro loss - an thrilling contest with Callum Smith in February - to secure a 20th pro success.
Various analysts thought Parker, thirty-one, merited the decision but the Derbyshire fighter suffered the second loss of his 28-bout professional journey.
The Champion Secures Triumph in Dull Encounter
Buatsi's progress has stalled in the past few years through contract problems and long spells of inactivity.
Earlier forecast as the rising talent of British boxing, he now stands trying to achieve expectations - perhaps in what seems like a final roll of the dice - under new promotional backing.
He started carefully, with the two boxers willing to take risks in a cagey opening few rounds.
Parker, whose only previous defeat came at the lower weight class against his former opponent in two years ago after suffering a hand injury mid-fight, was participating in his second appearance at light heavyweight.
By the halfway stage, the underdog had kept it close, making life awkward for Buatsi, who operated with a protective stance to narrowly win the better stanzas.
The spectators' acceptance diminished amid constant clinching, with the challenger falling to the floor several times during close exchanges.
Parker finished the stronger, but many rounds were challenging to assess. Nevertheless, ex-champion Carl Frampton - working with Dazn - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
The victor advances, but with the likes of power puncher David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Hatton Tribute Fuels Manchester Derby Battle
In the secondary fight, Lyndon Arthur defeated Bradley Rea by close verdict in a terrific Manchester vs Manchester fight to secure the European light heavyweight championship.
The venue grew hushed for a deeply poignant memorial prior to the bout as a bell ceremony tolled in memory of the city's native Ricky Hatton, who succumbed 46 years old in last month.
It was the first major televised boxing event in the location since the passing of Hatton. As the concluding sound faded, the stillness transitioned to a roar of "there's just one Ricky Hatton".
The action within the ring matched the feeling. Arthur was floored by a left hook flush on the face in the early round, standing uncertainly to his position on the eight count.
But the traditional red attire of Arthur soon came forward again. Across the ring, Rea - in competitive blue - was marked up quickly, noticeable damage developing under his orbital area as the pair exchanged hard punches.
Rea, twenty-seven, connected with strong blows but Arthur, 34, responded in kind with powerful upward punches as the action seldom decreased over the full distance.
Arthur edged the decision with scoring tallies of draw, narrow lead and wider gap, but the two athletes were relentless and full of heart, everything their hero Hatton embodied.
