UK light-heavyweight Buatsi secured a victory yet unimpressive beginning to his career under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a split decision in a competitive 10-round bout at the Manchester venue.
But the challenger landed significant shots, delivering effective single shots in a match where the styles failed to mesh, with frequent clinching marring the action.
The officials had it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my greatest display but what do champions do? They win," Buatsi commented in the ringside as he was met by negative reactions from the spectators.
The British fighter got back to winning after his first professional defeat - an epic battle with Callum Smith in last winter - to claim a 20th career victory.
Several boxing experts felt Parker, 31, should have been awarded the decision but the contender experienced the second loss of his 28-bout professional journey.
Buatsi Claims Victory in Slow Affair
Buatsi's progress has stalled in recent years through contract problems and long spells of inactivity.
Once tipped as the next star of UK boxing, he now is positioned trying to realize his potential - perhaps in what feels like a last chance - under fresh management.
He started carefully, with the two boxers prepared to take risks in a calculated opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in 2022 after suffering a hand injury during the bout, was competing in only his second appearance at light heavyweight.
By the middle rounds, the underdog had stayed in contention, making life awkward for Buatsi, who worked behind a solid defense to narrowly win the cleaner stanzas.
The crowd's patience decreased amid frequent holding, with the challenger slipping to the canvas multiple occasions 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 the challenger, awarding Buatsi just one round.
Buatsi advances, but with the presence of hard hitter Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - judging by this showing - still appears challenging.
Ricky Hatton Homage Fuels Local Rivalry Fight
In the secondary fight, Lyndon Arthur overcame Bradley Rea by split-decision in a outstanding Manchester vs Manchester fight to capture the European light-heavyweight belt.
The arena fell silent for a deeply poignant tribute prior to the bout as 10 bells sounded in remembrance of Manchester's own Hatton, who succumbed aged 46 in September.
It was the first major televised match card in the city since Hatton's passing. As the last bell ended, the stillness gave way to a roar of "only one Ricky Hatton".
The fighting within the ring matched the feeling. Arthur was sent to the canvas by a left hook directly to the chin in the early round, rising shakily to his footing on the count of eight.
But the traditional red shorts of the fighter soon came forward again. Across the ring, Rea - in opposing blue - was marked up early, significant bruising appearing under his face as the pair exchanged punishing blows.
Rea, twenty-seven, landed power punches but the champion, thirty-four, fought fire with fire with powerful upward punches as the intensity seldom decreased over 12 rounds.
Arthur edged the result with official scores of draw, close margin and clearer margin, but both fighters were determined and brave, exactly what their idol Hatton represented.
