British light heavyweight Buatsi made a winning yet disappointing beginning to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a competitive 10-round fight at the Manchester venue.
But Parker found success, landing some telling single shots in a contest where the techniques failed to mesh, with constant grabbing spoiling the contest.
Two judges judged it 96-94 to the winner, with the remaining official a even score.
"It wasn't my greatest showing but how do champions respond? They prevail," Buatsi stated in the ringside as he was faced negative reactions from the audience.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in last winter - to secure a 20th pro success.
Various analysts thought the challenger, thirty-one, deserved the win but the British boxer endured the second setback of his 28-fight career.
The Champion Claims Win in Uneventful Match
His career development has stalled in the past few years through contract problems and considerable time of lack of fights.
Earlier forecast as the next star of the British fight scene, he now finds himself trying to achieve expectations - possibly in what seems like a last chance - under new promotional backing.
He began cautiously, with neither fighter ready to be aggressive in a tentative early stages.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after damaging his hand in the contest, was competing in only his second appearance at light-heavyweight.
By the middle rounds, Parker had made it competitive, causing problems for the favorite, who worked behind a solid defense to barely take the better rounds.
The crowd's patience diminished because of constant clinching, with Parker slipping to the canvas several times during close exchanges.
Parker finished the stronger, but several stanzas were challenging to assess. Nevertheless, ex-champion the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
The victor progresses, but with the caliber of hard hitter Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Memorial Inspires Manchester Derby Fight
In the secondary fight, Arthur beat Rea by split-decision in a terrific local rivalry contest to win the European light-heavyweight belt.
The venue grew hushed for a profoundly moving tribute prior to the bout as 10 bells tolled in honor of Manchester's own Hatton, who passed away at age 46 in September.
It was the first major televised boxing event in the location since the passing of Hatton. As the last bell ended, the quiet gave way to a shout of "only one Ricky Hatton".
The competition within the ring matched the emotion. The eventual winner was floored by a significant blow squarely on the chin in the initial stage, standing uncertainly to his footing on the count of eight.
But the Manchester United-red equipment of the fighter soon advanced again. On the opposite side, the opponent - in opposing blue - was injured soon, significant bruising appearing under his face as the duo exchanged punishing blows.
Rea, 27, connected with strong blows but Arthur, thirty-four, responded in kind with stinging uppercuts as the pace rarely dropped over the full distance.
The victor barely secured the verdict with scoring tallies of 114-114, close margin and clearer margin, but both fighters were persistent and full of heart, all the qualities their idol the legend stood for.
