UK light-heavyweight Buatsi secured a victory yet unimpressive beginning to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a judges' verdict in a tight ten-round contest at the Co-op Live Arena.
But Parker found success, landing some telling clean blows in a contest where the techniques didn't complement each other, with constant grabbing disrupting the action.
The scoring judges scored it 96-94 for to the winner, with the third a even score.
"It wasn't my best performance but how do champions respond? They prevail," the victor said in the ringside as he was greeted with disapproval from the spectators.
The Londoner bounced back after his initial pro loss - an epic battle with Callum Smith in last winter - to secure a 20th pro success.
Various analysts felt the challenger, 31, should have been awarded the decision but the British boxer endured the second loss of his 28-fight career.
Buatsi Earns Victory in Slow Affair
His career development has stalled in recent years through management issues and considerable time of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now finds himself trying to realize his potential - possibly in what appears to be a final roll of the dice - under fresh management.
He began cautiously, with the two boxers prepared to be aggressive in a cagey initial rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in two years ago after damaging his hand in the contest, was making just his second appearance at light-heavyweight.
By the middle rounds, Parker had kept it close, creating difficulties for Buatsi, who utilized a tight guard to edge the more effective periods.
The crowd's patience diminished because of constant clinching, with Parker slipping to the canvas multiple occasions during grappling.
The underdog closed well, but multiple periods were challenging to assess. Although, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the presence of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the road to world glory - on this evidence - still looks steep.
Hatton Memorial Motivates Local Rivalry Contest
In the secondary fight, Arthur beat Rea by close verdict in a terrific Manchester vs Manchester battle to capture the European light-heavyweight championship.
The venue became quiet for a extremely emotional homage prior to the bout as 10 bells rang in remembrance of Manchester's own Hatton, who died at age 46 in last month.
It was the initial significant broadcast fight night in the city since the passing of Hatton. As the last bell faded, the quiet transitioned to a shout of "there's only one Hatton".
The action inside the ropes equaled the feeling. Arthur was floored by a significant blow flush on the chin in the second round, getting up unsteadily to his feet on the referee's count.
But the red-colored shorts of Arthur soon pressed ahead again. From the other corner, Rea - in competitive blue - was injured early, noticeable damage appearing under his face as the fighters landed hard punches.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, matched the intensity with effective uppercuts as the intensity seldom decreased over twelve rounds.
Arthur barely secured the decision with official scores of 114-114, 115-113 and clearer margin, but the two athletes were persistent and brave, exactly what their inspiration the legend represented.
