UK 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 bronze medallist's punch output appeared to earn him a split decision in a competitive ten-round fight at the boxing arena.
But Parker found success, landing some telling individual punches in a match where the styles failed to mesh, with frequent clinching marring the contest.
The scoring judges had it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my greatest display but how do champions respond? They succeed," Buatsi said in the arena as he was met by boos from the crowd.
The Londoner got back to winning after his first professional defeat - an thrilling contest with Callum Smith in February - to claim a twentieth professional win.
Various analysts thought the challenger, thirty-one, merited the win but the Derbyshire fighter experienced the second loss of his 28-match professional journey.
Buatsi Earns Triumph in Uneventful Affair
The fighter's advancement has stalled in the past few years through management issues and extended periods of inactivity.
Previously predicted as the future of British boxing, he now is positioned trying to realize his potential - perhaps in what seems like a last chance - under fresh management.
He began cautiously, with the two boxers ready to overcommit in a tentative opening few rounds.
Parker, whose sole prior loss came at super middleweight against John Ryder in 2022 after damaging his hand in the contest, was participating in his second bout at light heavyweight.
By the halfway stage, the underdog had made it competitive, causing problems for the favorite, who utilized a tight guard to barely take the cleaner stanzas.
The crowd's patience diminished because of constant clinching, with Parker slipping to the canvas multiple occasions during close exchanges.
Parker ended stronger, but multiple periods were difficult to score. Although, previous titleholder the boxing analyst - working with Dazn - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the presence of hard hitter David Benavidez, and Russian champion Bivol leading the category, the journey to titles - on this evidence - still looks steep.
Ricky Hatton Tribute Fuels All-Manchester Fight
In the supporting bout, Lyndon Arthur beat Rea by split-decision in a terrific local rivalry battle to secure the continental championship.
The stadium grew hushed for a profoundly moving tribute prior to the bout as ten bells rang in remembrance of Manchester's own Hatton, who passed away at age 46 in last month.
It was the premier televised fight night in the location since Hatton's death. As the concluding sound faded, the quiet transitioned to a chant of "only one Hatton".
The fighting during the bout reflected the sentiment. Arthur was floored by a powerful punch directly to the chin in the initial stage, rising shakily to his position on the eight count.
But the traditional red attire of Arthur soon pressed ahead again. Across the ring, the opponent - in opposing blue - was damaged quickly, heavy swelling forming under his face as the pair landed punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, fought fire with fire with stinging uppercuts as the intensity hardly diminished over 12 rounds.
The victor barely secured the verdict with official scores of even score, close margin and wider gap, but the two athletes were persistent and full of heart, everything their idol the legend stood for.
