British light heavyweight Buatsi secured a victory yet underwhelming beginning to his career under fresh promotional backing with a unanimous decision 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 Manchester venue.
But Parker found success, delivering effective single shots in a match where the techniques failed to mesh, with frequent clinching marring the fight.
Two judges had it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my finest display but what do champions do? They win," the victor commented in the ringside as he was greeted with boos from the spectators.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in last winter - to earn a 20th career victory.
Several boxing experts felt Parker, 31, merited the win but the British boxer experienced the second loss of his 28-fight professional journey.
Buatsi Earns Victory in Uneventful Encounter
Buatsi's progress has slowed in recent times through management issues and extended periods of lack of fights.
Once tipped as the future of UK boxing, he now is positioned trying to fulfil that early promise - possibly in what appears to be a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter willing to take risks in a cagey opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after breaking his hand during the bout, was making just his second fight at the higher weight class.
By the middle rounds, the underdog had stayed in contention, making life awkward for Buatsi, who worked behind a tight guard to edge the cleaner stanzas.
The audience's tolerance decreased amid constant clinching, with Parker falling to the floor various instances during close exchanges.
Parker finished the stronger, but several stanzas were hard to judge. Nevertheless, previous titleholder Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, scoring for Buatsi just one round.
Buatsi progresses, but with the presence of hard hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - based on this performance - still appears challenging.
Ricky Hatton Tribute Inspires Local Rivalry Battle
In the co-main event, Arthur overcame Rea by close verdict in a outstanding all-Manchester fight to win the continental title.
The venue became quiet for a profoundly moving homage before the fight as a bell ceremony sounded in remembrance of Manchester's own Ricky Hatton, who died aged 46 in recently.
It was the first major televised fight night in the location since the passing of Hatton. As the last bell faded, the quiet gave way to a shout of "there's just one Hatton".
The fighting within the ring equaled the sentiment. Arthur was sent to the canvas by a powerful punch directly to the chin in the second round, rising shakily to his footing on the referee's count.
But the traditional red attire of the fighter soon came forward again. Across the ring, Rea - in rival City blue - was damaged soon, noticeable damage appearing under his face as the duo landed hard punches.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, matched the intensity with effective uppercuts as the pace seldom decreased over twelve rounds.
The victor barely secured the result with official scores of draw, 115-113 and wider gap, but each competitor were persistent and full of heart, all the qualities their idol the legend stood for.
