British light-heavyweight Buatsi secured a victory yet underwhelming debut to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a split decision in a close 10-round contest at the boxing arena.
But the challenger found success, delivering effective clean blows in a fight where the styles failed to mesh, with frequent clinching marring the fight.
The scoring judges judged it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They prevail," Buatsi stated in the ringside as he was greeted with boos from the spectators.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in February - to earn a 20th career victory.
Some ringside observers felt the challenger, 31, deserved the win but the British boxer endured the second setback of his 28-fight professional journey.
The Champion Earns Triumph in Uneventful Affair
His career development has stalled in recent times through promotional disputes and considerable time of inactivity.
Earlier forecast as the future of British boxing, he now is positioned trying to fulfil that early promise - possibly in what feels like a last chance - under recent support.
He began cautiously, with both competitors willing to take risks in a cagey initial rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in 2022 after damaging his hand in the contest, was participating in his second appearance at the higher weight class.
By the middle rounds, Parker had made it competitive, causing problems for Buatsi, who operated with a tight guard to barely take the more effective periods.
The audience's tolerance diminished because of constant clinching, with the challenger slipping to the canvas several times during grappling.
Parker closed well, but several stanzas were challenging to assess. Although, ex-champion Carl Frampton - commentating on Dazn - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
Buatsi advances, but with the caliber of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still appears challenging.
Hatton Homage Fuels Local Rivalry Fight
In the co-main event, Lyndon Arthur defeated Rea by divided decision in a outstanding Manchester vs Manchester contest to secure the European light-heavyweight championship.
The venue became quiet for a deeply poignant homage ahead of the contest as 10 bells tolled in remembrance of Manchester's own Ricky Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast match card in the city since Hatton's death. As the last bell ended, the quiet transitioned to a shout of "only one Hatton".
The action during the bout matched the feeling. Arthur was floored by a significant blow flush on the jaw in the early round, rising shakily to his position on the count of eight.
But the Manchester United-red attire of the fighter soon pressed ahead again. Across the ring, Rea - in opposing blue - was marked up soon, heavy swelling appearing under his orbital area as the duo traded punishing blows.
The challenger, 27, connected with strong blows but the champion, 34, fought fire with fire with stinging uppercuts as the pace rarely dropped over 12 rounds.
The victor narrowly won the result with judges scorecards of 114-114, 115-113 and wider gap, but each competitor were persistent and courageous, exactly what their inspiration Hatton stood for.
