British light-heavyweight Buatsi made a winning yet unimpressive beginning to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output likely gained him a majority decision in a close 10-round bout at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling clean blows in a fight where the approaches didn't complement each other, with frequent clinching spoiling the contest.
The officials judged it 96-94 to Buatsi, with the third a 95-95.
"It wasn't my finest showing but what defines champions? They win," the victor stated in the ringside as he was faced boos from the spectators.
The Londoner returned to winning ways after his first professional defeat - an epic battle with his previous opponent in February - to claim a 20th career victory.
Several boxing experts thought Parker, thirty-one, merited the decision but the Derbyshire fighter endured the second defeat of his 28-match professional journey.
Buatsi Claims Win in Slow Encounter
His career development has plateaued in recent years through promotional disputes and considerable time of inactivity.
Once tipped as the next star of UK boxing, he now finds himself trying to achieve expectations - maybe in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with neither fighter willing to overcommit in a tentative opening few rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was making just his second appearance at the higher weight class.
By the middle rounds, Parker had kept it close, causing problems for the favorite, who worked behind a solid defense to narrowly win the cleaner periods.
The audience's tolerance wore thin amid regular grabbing, with the challenger falling to the floor several times during grappling.
The underdog closed well, but multiple periods were difficult to score. Although, former world champion the boxing analyst - working with Dazn - had it significantly in favor for Parker, giving Buatsi just one round.
Buatsi moves on, but with the caliber of power puncher Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - based on this performance - still appears challenging.
Hatton Memorial Inspires All-Manchester Fight
In the secondary fight, Lyndon Arthur overcame Bradley Rea by close verdict in a outstanding Manchester vs Manchester battle to capture the European light-heavyweight championship.
The venue grew hushed for a deeply poignant memorial before the fight as 10 bells tolled in honor of local hero Ricky Hatton, who succumbed aged 46 in September.
It was the initial significant broadcast match card in the location since the passing of Hatton. As the last bell ended, the silence became a roar of "only one Ricky Hatton".
The competition during the bout reflected the sentiment. Arthur was sent to the canvas by a powerful punch squarely on the chin in the second round, getting up unsteadily to his feet on the count of eight.
But the Manchester United-red attire of Arthur soon came forward again. From the other corner, Rea - in competitive blue - was marked up soon, heavy swelling developing under his face as the fighters landed powerful shots.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with powerful upward punches as the pace hardly diminished over the full distance.
The victor narrowly won the verdict with official scores of draw, close margin and 115-112, but each competitor were persistent and brave, everything their inspiration the legend represented.
