UK light-heavyweight Buatsi earned a win yet disappointing beginning to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a judges' verdict in a tight 10-round fight at the boxing arena.
But Parker found success, delivering effective single shots in a match where the approaches failed to mesh, with frequent clinching spoiling the action.
The officials judged it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my finest display but what do champions do? They prevail," Buatsi said in the ringside as he was met by disapproval from the spectators.
The Londoner got back to winning after his first professional defeat - an thrilling contest with Callum Smith in last winter - to claim a twentieth professional win.
Several boxing experts felt Parker, thirty-one, should have been awarded the victory but the British boxer endured the second setback of his 28-bout professional journey.
Buatsi Claims Triumph in Dull Affair
Buatsi's progress has plateaued in the past few years through management issues and extended periods of lack of fights.
Earlier forecast as the rising talent of British boxing, he now finds himself trying to realize his potential - perhaps in what seems like a final roll of the dice - under recent support.
He opened tentatively, with the two boxers ready to overcommit in a calculated early stages.
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 fight at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, making life awkward for Buatsi, who utilized a tight guard to narrowly win the cleaner rounds.
The crowd's patience diminished during frequent holding, with the challenger going down multiple occasions during clinches.
The underdog ended stronger, but multiple periods were challenging to assess. Although, ex-champion Carl Frampton - commentating on the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
The victor progresses, but with the presence of heavy hitter Benavidez, and Eastern European fighter Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Hatton Memorial Inspires Local Rivalry Fight
In the secondary fight, Arthur beat Bradley Rea by divided decision in a outstanding Manchester vs Manchester fight to secure the continental title.
The stadium grew hushed for a profoundly moving tribute prior to the bout as ten bells tolled in memory of local hero Ricky Hatton, who passed away 46 years old in recently.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the last bell ended, the silence gave way to a chant of "only one Hatton".
The competition during the bout reflected the sentiment. Arthur was sent to the canvas by a left hook squarely on the face in the initial stage, getting up unsteadily to his footing on the referee's count.
But the traditional red equipment of the fighter soon came forward again. On the opposite side, the opponent - in competitive blue - was injured quickly, heavy swelling developing under his eye as the pair traded hard punches.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, fought fire with fire with effective uppercuts as the intensity seldom decreased over 12 rounds.
Arthur barely secured the decision with official scores of even score, 115-113 and 115-112, but the two athletes were relentless and full of heart, all the qualities their hero Hatton stood for.
