UK light heavyweight Buatsi made a winning yet disappointing debut to life under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a split decision in a close ten-round bout at the boxing arena.
But Parker landed significant shots, delivering effective single shots in a fight where the styles never quite clicked, with constant grabbing marring the contest.
The scoring judges judged it 96-94 in favor to Buatsi, with the final judge a 95-95.
"It wasn't my finest showing but what do champions do? They prevail," Buatsi commented in the arena as he was faced negative reactions from the crowd.
The Londoner bounced back after his initial pro loss - an epic battle with his previous opponent in February - to secure a 20th career victory.
Several boxing experts felt the challenger, 31, should have been awarded the win but the British boxer endured the second defeat of his 28-bout professional journey.
The Champion Claims Victory in Dull Affair
Buatsi's progress has stalled in the past few years through contract problems and considerable time of inactivity.
Previously predicted as the rising talent of the British fight scene, he now finds himself trying to realize his potential - maybe in what feels like a last chance - under new promotional backing.
He started carefully, with neither fighter willing to overcommit in a tentative opening few rounds.
Parker, whose sole prior loss came at the lower weight class against his former opponent in two years ago after suffering a hand injury mid-fight, was making just his second fight at the higher weight class.
By the fight's midpoint, Parker had made it competitive, making life awkward for the favorite, who operated with a protective stance to barely take the cleaner periods.
The crowd's patience diminished during frequent holding, with the challenger going down various instances during grappling.
The underdog finished the stronger, but many rounds were challenging to assess. However, ex-champion the boxing analyst - commentating on Dazn - had it significantly in favor for Parker, scoring for Buatsi just a single round.
The victor progresses, but with the presence of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Tribute Fuels Local Rivalry Contest
In the supporting bout, Lyndon Arthur beat Rea by close verdict in a terrific local rivalry fight to secure the continental championship.
The stadium fell silent for a profoundly moving homage ahead of the contest as a bell ceremony tolled in remembrance of the city's native Hatton, who died at age 46 in September.
It was the initial significant broadcast match card in the location since Hatton's passing. As the last bell ended, the silence transitioned to a chant of "there's just one Ricky Hatton".
The action during the bout equaled the emotion. The eventual winner was sent to the canvas by a significant blow flush on the face in the initial stage, getting up unsteadily to his feet on the count of eight.
But the traditional red shorts of Arthur soon advanced again. On the opposite side, Rea - in rival City blue - was marked up early, heavy swelling developing under his orbital area as the fighters exchanged hard punches.
The challenger, 27, landed power punches but Arthur, 34, responded in kind with powerful upward punches as the action rarely dropped over 12 rounds.
The victor narrowly won the result with judges scorecards of draw, narrow lead and 115-112, but each competitor were relentless and full of heart, exactly what their idol Hatton embodied.
