British light-heavyweight Buatsi made a winning yet unimpressive start to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a competitive 10-round contest at the Co-op Live Arena.
But the challenger landed significant shots, connecting with powerful individual punches in a fight where the techniques failed to mesh, with frequent clinching spoiling the fight.
The scoring judges had it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my best performance but how do champions respond? They win," Buatsi stated in the arena as he was greeted with negative reactions from the spectators.
The Londoner got back to winning after his initial pro loss - an epic battle with Callum Smith in February - to earn a twentieth professional win.
Various analysts believed the challenger, thirty-one, merited the victory but the British boxer endured the second defeat of his 28-match career.
The Champion Secures Win in Uneventful Match
Buatsi's progress has slowed in the past few years through management issues and extended periods of inactivity.
Once tipped as the rising talent of UK boxing, he now finds himself trying to realize his potential - maybe in what appears to be a last chance - under new promotional backing.
He started carefully, with the two boxers prepared to overcommit in a cagey opening few rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after damaging his hand mid-fight, was competing in only his second fight at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, making life awkward for Buatsi, who operated with a protective stance to narrowly win the more effective rounds.
The audience's tolerance decreased amid regular grabbing, with Parker slipping to the canvas various instances during close exchanges.
Parker ended stronger, but several stanzas were challenging to assess. Although, former world champion Carl Frampton - working with the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just one round.
The victor advances, but with the likes of power puncher Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - based on this performance - still looks steep.
Hatton Tribute Fuels Local Rivalry Battle
In the co-main event, Arthur defeated Bradley Rea by divided decision in a terrific local rivalry fight to secure the continental championship.
The stadium became quiet for a profoundly moving homage ahead of the contest as 10 bells tolled in honor of local hero Ricky Hatton, who passed away aged 46 in last month.
It was the first major televised boxing event in the location since Hatton's passing. As the concluding sound ended, the stillness transitioned to a shout of "there's just one Hatton".
The fighting during the bout matched the emotion. The eventual winner was floored by a left hook squarely on the face in the second round, getting up unsteadily to his position on the referee's count.
But the red-colored equipment of Arthur soon advanced again. On the opposite side, Rea - in opposing blue - was marked up quickly, noticeable damage appearing under his face as the duo traded hard punches.
Rea, 27, delivered effective strikes but the champion, thirty-four, responded in kind with effective uppercuts as the intensity hardly diminished over the full distance.
Arthur edged the result with scoring tallies of draw, 115-113 and wider gap, but each competitor were determined and brave, all the qualities their hero the legend embodied.
