UK light-heavyweight Buatsi earned a win yet unimpressive beginning to his career under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a majority decision in a competitive 10-round fight at the Co-op Live Arena.
But Parker found success, landing some telling single shots in a match where the styles failed to mesh, with frequent clinching disrupting the contest.
The scoring judges scored it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my best showing but how do champions respond? They win," Buatsi stated in the ring as he was faced disapproval from the spectators.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in last winter - to earn a 20th pro success.
Several boxing experts felt the challenger, thirty-one, deserved the decision but the Derbyshire fighter suffered the second loss of his 28-bout career.
Buatsi Claims Triumph in Uneventful Affair
His career development has plateaued in recent years through contract problems and extended periods of inactivity.
Earlier forecast as the next star of UK boxing, he now stands trying to achieve expectations - perhaps in what appears to be a ultimate opportunity - under recent support.
He began cautiously, with the two boxers ready to be aggressive in a calculated early stages.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in two years ago after breaking his hand mid-fight, was competing in only his second appearance at light-heavyweight.
By the middle rounds, Parker had stayed in contention, creating difficulties for Buatsi, who worked behind a solid defense to barely take the more effective periods.
The crowd's patience decreased amid constant clinching, with Parker falling to the floor several times during close exchanges.
Parker ended stronger, but many rounds were challenging to assess. Although, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, awarding Buatsi just one round.
Buatsi moves on, but with the caliber of heavy hitter Benavidez, and Eastern European fighter Bivol ruling the division, the journey to titles - on this evidence - still looks steep.
Hatton Memorial Inspires Manchester Derby Fight
In the co-main event, Lyndon Arthur beat Bradley Rea by divided decision in a terrific all-Manchester fight to secure the European light-heavyweight championship.
The arena grew hushed for a deeply poignant memorial before the fight as 10 bells rang in memory of the city's native Ricky Hatton, who passed away at age 46 in September.
It was the initial significant broadcast boxing event in the location since Hatton's passing. As the last bell faded, the silence became a shout of "there's only one Hatton".
The competition during the bout reflected the feeling. The eventual winner was sent to the canvas by a left hook flush on the jaw in the early round, rising shakily to his feet on the count of eight.
But the Manchester United-red attire of the fighter soon advanced again. Across the ring, Rea - in rival City blue - was marked up quickly, significant bruising developing under his orbital area as the pair exchanged hard punches.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with effective uppercuts as the action seldom decreased over twelve rounds.
Arthur narrowly won the verdict with official scores of 114-114, 115-113 and 115-112, but both fighters were persistent and full of heart, exactly what their idol the legend represented.
