British light heavyweight Buatsi secured a victory yet underwhelming debut to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output likely gained him a judges' verdict in a competitive ten-round bout at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful single shots in a contest where the styles failed to mesh, with constant grabbing disrupting the fight.
Two judges had it 96-94 to Buatsi, with the third a even score.
"It wasn't my finest showing but what defines champions? They succeed," the victor stated in the ringside as he was met by negative reactions from the crowd.
The Londoner got back to winning after his initial pro loss - an thrilling contest with Callum Smith in last winter - to claim a 20th career victory.
Some ringside observers felt the challenger, thirty-one, should have been awarded the decision but the Derbyshire fighter endured the second defeat of his 28-fight professional journey.
The Champion Claims Win in Dull Match
The fighter's advancement has plateaued in the past few years through management issues and considerable time of inactivity.
Earlier forecast as the next star of British boxing, he now stands trying to fulfil that early promise - maybe in what feels like a last chance - under recent support.
He began cautiously, with neither fighter ready to be aggressive in a cagey opening few rounds.
Parker, whose sole prior loss came at the lower weight class against his former opponent in two years ago after breaking his hand during the bout, was making just his second fight at light-heavyweight.
By the middle rounds, Parker had stayed in contention, making life awkward for the favorite, who worked behind a tight guard to edge the more effective periods.
The crowd's patience diminished during constant clinching, with Parker going down several times during clinches.
Parker ended stronger, but several stanzas were hard to judge. Although, previous titleholder the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi progresses, but with the likes of hard hitter David Benavidez, and Russian star Bivol leading the category, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Homage Motivates All-Manchester Battle
In the secondary fight, Lyndon Arthur overcame Bradley Rea by divided decision in a terrific all-Manchester battle to capture the European light-heavyweight belt.
The stadium grew hushed for a profoundly moving memorial before the fight as a bell ceremony tolled in honor of Manchester's own Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast boxing event in the city since Hatton's passing. As the concluding sound faded, the quiet became a roar of "there's just one Ricky Hatton".
The action during the bout reflected the feeling. Arthur was sent to the canvas by a left hook directly to the chin in the second round, rising shakily to his position on the eight count.
But the traditional red equipment of Arthur soon advanced again. On the opposite side, the opponent - in opposing blue - was damaged early, heavy swelling appearing under his eye as the duo traded punishing blows.
Rea, twenty-seven, landed power punches but the champion, 34, matched the intensity with powerful upward punches as the intensity seldom decreased over twelve rounds.
The victor narrowly won the result with scoring tallies of draw, narrow lead and clearer margin, but the two athletes were determined and brave, all the qualities their hero Hatton stood for.
