British light-heavyweight Buatsi made a winning yet unimpressive beginning to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a majority decision in a tight ten-round bout at the Co-op Live Arena.
But Parker had his moments, landing some telling single shots in a match where the techniques failed to mesh, with constant grabbing spoiling the contest.
Two judges scored it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my best display but what defines champions? They win," Buatsi commented in the ringside as he was faced negative reactions from the crowd.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Various analysts thought Parker, 31, should have been awarded the victory but the Derbyshire fighter suffered the second loss of his 28-match professional journey.
The Champion Earns Triumph in Slow Match
His career development has stalled in recent years through promotional disputes and long spells of inactivity.
Earlier forecast as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under recent support.
He started carefully, with neither fighter prepared to take risks in a calculated early stages.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after damaging his hand during the bout, was making just his second fight at light heavyweight.
By the middle rounds, Parker had kept it close, making life awkward for the favorite, who operated with a solid defense to barely take the cleaner stanzas.
The crowd's patience wore thin amid regular grabbing, with Parker falling to the floor various instances during grappling.
Parker closed well, but multiple periods were challenging to assess. However, previous titleholder Carl Frampton - commentating on Dazn - had it strongly leaning for Parker, scoring for Buatsi just a single round.
The victor progresses, but with the likes of heavy hitter Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - based on this performance - still appears challenging.
Hatton Homage Inspires All-Manchester Contest
In the secondary fight, Arthur beat Bradley Rea by divided decision in a excellent local rivalry contest to win the European light-heavyweight championship.
The venue became quiet for a deeply poignant homage ahead of the contest as ten bells tolled in remembrance of the city's native Hatton, who died aged 46 in September.
It was the initial significant broadcast fight night in the city since Hatton's death. As the concluding sound disappeared, the stillness became a chant of "only one Hatton".
The competition during the bout equaled the sentiment. Arthur was sent to the canvas by a left hook directly to the jaw in the early round, rising shakily to his position on the count of eight.
But the traditional red shorts of Arthur soon advanced again. From the other corner, Rea - in rival City blue - was injured soon, significant bruising developing under his eye as the fighters exchanged powerful shots.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, matched the intensity with stinging uppercuts as the action seldom decreased over 12 rounds.
Arthur edged the result with scoring tallies of draw, narrow lead and clearer margin, but both fighters were determined and brave, all the qualities their hero Hatton stood for.
