UK light heavyweight Buatsi earned a win yet underwhelming beginning to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output likely gained him a judges' verdict in a tight 10-round bout at the Co-op Live Arena.
But Parker found success, connecting with powerful single shots in a contest where the approaches never quite clicked, with excessive holding marring the action.
The scoring judges judged it 96-94 for to the winner, with the third a even score.
"It wasn't my finest showing but how do champions respond? They win," Buatsi stated in the arena as he was faced disapproval from the crowd.
The British fighter got back to winning after his first professional defeat - an thrilling contest with his previous opponent in February - to secure a twentieth professional win.
Various analysts felt the challenger, thirty-one, deserved the decision but the British boxer experienced the second setback of his 28-match professional journey.
The Champion Secures Win in Uneventful Affair
His career development has stalled in recent times through contract problems and considerable time of lack of fights.
Earlier forecast as the next star of UK boxing, he now is positioned trying to achieve expectations - maybe in what seems like a final roll of the dice - under new promotional backing.
He opened tentatively, with both competitors ready to overcommit in a tentative initial rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in two years ago after suffering a hand injury in the contest, was participating in his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, creating difficulties for the favorite, who utilized a solid defense to edge the cleaner stanzas.
The crowd's patience wore thin during constant clinching, with the challenger going down several times during grappling.
Parker closed well, but multiple periods were challenging to assess. Nevertheless, previous titleholder the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, scoring for Buatsi just a single round.
The victor advances, but with the presence of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Homage Fuels Manchester Derby Battle
In the co-main event, Arthur defeated Rea by close verdict in a terrific all-Manchester fight to secure the European light-heavyweight belt.
The arena became quiet for a profoundly moving homage prior to the bout as ten bells rang in honor of Manchester's own Ricky Hatton, who passed away at age 46 in recently.
It was the premier televised fight night in the location since the passing of Hatton. As the concluding sound faded, the silence transitioned to a roar of "there's only one Hatton".
The action inside the ropes reflected the feeling. Arthur was floored by a powerful punch flush on the jaw in the second round, rising shakily to his feet on the referee's count.
But the red-colored equipment of the fighter soon came forward again. Across the ring, the opponent - in competitive blue - was damaged early, significant bruising forming under his face as the pair traded hard punches.
The challenger, 27, landed power punches but the champion, 34, matched the intensity with stinging uppercuts as the pace rarely dropped over the full distance.
Arthur edged the result with judges scorecards of draw, close margin and clearer margin, but the two athletes were persistent and brave, everything their idol Hatton represented.
