UK light-heavyweight Buatsi made a winning yet unimpressive start 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 10-round fight at the Manchester venue.
But the challenger landed significant shots, connecting with powerful individual punches in a contest where the approaches didn't complement each other, with excessive holding marring the contest.
The scoring judges scored it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my finest display but what do champions do? They prevail," Buatsi stated in the arena as he was greeted with disapproval from the spectators.
The British fighter got back to winning after his maiden career setback - an epic battle with his previous opponent in February - to earn a twentieth professional win.
Several boxing experts thought Parker, thirty-one, should have been awarded the victory but the contender experienced the second loss of his 28-match professional journey.
Buatsi Claims Triumph in Uneventful Match
His career development has plateaued in recent times through promotional disputes and long spells of lack of fights.
Once tipped as the rising talent of British boxing, he now is positioned trying to achieve expectations - possibly in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with both competitors ready to take risks in a tentative opening few rounds.
Parker, whose only previous defeat came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was competing in only his second bout at light heavyweight.
By the middle rounds, Parker had kept it close, making life awkward for Buatsi, who worked behind a tight guard to edge the better rounds.
The crowd's patience wore thin during frequent holding, with the challenger going down various instances during close exchanges.
The underdog closed well, but many rounds were hard to judge. However, ex-champion the boxing analyst - 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 star Bivol dominating the weight class, the path to championship success - based on this performance - still looks steep.
Hatton Tribute Inspires All-Manchester Contest
In the secondary fight, Arthur beat Bradley Rea by divided decision in a terrific all-Manchester battle to secure the European light heavyweight title.
The stadium became quiet for a extremely emotional memorial prior to the bout as 10 bells tolled in remembrance of local hero Hatton, who passed away aged 46 in September.
It was the initial significant broadcast boxing event in the location since the passing of Hatton. As the final chime ended, the quiet gave way to a chant of "only one Ricky Hatton".
The action during the bout equaled the sentiment. Arthur was knocked down by a left hook directly to the chin in the initial stage, standing uncertainly to his footing on the count of eight.
But the traditional red equipment of Arthur soon pressed ahead again. From the other corner, Rea - in opposing blue - was marked up early, significant bruising appearing under his eye as the duo exchanged hard punches.
The challenger, 27, landed power punches but the champion, thirty-four, matched the intensity with powerful upward punches as the intensity hardly diminished over 12 rounds.
Arthur edged the result with scoring tallies of 114-114, 115-113 and 115-112, but both fighters were determined and brave, exactly what their hero the legend stood for.
