UK light-heavyweight Buatsi earned a win yet unimpressive 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 ten-round bout at the boxing arena.
But Parker landed significant shots, landing some telling single shots in a contest where the styles never quite clicked, with constant grabbing marring the fight.
The scoring judges judged it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my finest showing but how do champions respond? They succeed," Buatsi said in the ring as he was met by negative reactions from the spectators.
The British fighter bounced back after his maiden career setback - an thrilling contest with his previous opponent in last winter - to claim a 20th pro success.
Various analysts felt Parker, thirty-one, should have been awarded the victory but the Derbyshire fighter endured the second defeat of his 28-fight career.
Buatsi Claims Triumph in Slow Affair
The fighter's advancement has stalled in recent times through management issues and considerable time of inactivity.
Earlier forecast as the future of British boxing, he now stands trying to realize his potential - perhaps in what appears to be a final roll of the dice - under new promotional backing.
He began cautiously, with neither fighter ready to overcommit in a cagey initial rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second bout at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for the favorite, who utilized a tight guard to barely take the better rounds.
The spectators' acceptance decreased because of regular grabbing, with the challenger slipping to the canvas several times during clinches.
The underdog closed well, but several stanzas were challenging to assess. However, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi advances, but with the presence of heavy hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Tribute Motivates Local Rivalry Contest
In the supporting bout, Lyndon Arthur beat Bradley Rea by divided decision in a terrific Manchester vs Manchester fight to win the European light-heavyweight belt.
The venue became quiet for a extremely emotional homage before the fight as 10 bells tolled in memory of Manchester's own Ricky Hatton, who died 46 years old in September.
It was the first major televised match card in the urban center since Hatton's death. As the last bell faded, the silence gave way to a shout of "only one Hatton".
The fighting during the bout matched the emotion. The eventual winner was floored by a significant blow directly to the face in the early round, getting up unsteadily to his position on the referee's count.
But the Manchester United-red attire of the fighter soon pressed ahead again. From the other corner, the opponent - in opposing blue - was damaged early, noticeable damage appearing under his eye as the duo landed powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, 34, fought fire with fire with powerful upward punches as the intensity hardly diminished over 12 rounds.
The victor narrowly won the decision with judges scorecards of 114-114, 115-113 and wider gap, but the two athletes were persistent and full of heart, exactly what their hero the legend represented.
