British light heavyweight Buatsi earned a win yet disappointing start to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a majority decision in a tight 10-round fight at the boxing arena.
But the challenger found success, connecting with powerful single shots in a fight where the techniques failed to mesh, with frequent clinching disrupting the action.
Two judges scored it 96-94 in favor to Buatsi, with the final judge a 95-95.
"It wasn't my greatest display but what defines champions? They prevail," the victor commented in the ring as he was greeted with disapproval from the audience.
The British fighter got back to winning after his initial pro loss - an thrilling contest with Callum Smith in last winter - to earn a 20th career victory.
Some ringside observers believed the challenger, thirty-one, deserved the decision but the British boxer endured the second setback of his 28-fight professional journey.
Buatsi Secures Win in Dull Match
Buatsi's progress has plateaued in recent years through contract problems and considerable time of inactivity.
Once tipped as the future of the British fight scene, he now finds himself trying to realize his potential - perhaps in what seems like a last chance - under recent support.
He started carefully, with both competitors ready to be aggressive in a tentative opening few rounds.
The challenger, whose single earlier setback came at super middleweight against his former opponent in 2022 after breaking his hand mid-fight, was competing in only his second bout at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for Buatsi, who worked behind a solid defense to edge the cleaner rounds.
The crowd's patience decreased because of frequent holding, with the challenger slipping to the canvas various instances during grappling.
The underdog closed well, but several stanzas were challenging to assess. Although, former world champion the boxing analyst - commentating on Dazn - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the presence of power puncher Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still seems difficult.
Hatton Homage Inspires Manchester Derby Battle
In the supporting bout, Arthur overcame Bradley Rea by close verdict in a excellent all-Manchester contest to secure the continental championship.
The venue became quiet for a profoundly moving tribute ahead of the contest as ten bells sounded in honor of the city's native Ricky Hatton, who passed away aged 46 in recently.
It was the premier televised boxing event in the location since Hatton's death. As the concluding sound faded, the quiet became a roar of "there's just one Ricky Hatton".
The action during the bout matched the sentiment. The eventual winner was knocked down by a left hook flush on the jaw in the early round, standing uncertainly to his feet on the eight count.
But the red-colored equipment of the fighter soon pressed ahead again. From the other corner, Rea - in opposing blue - was injured quickly, significant bruising appearing under his face as the fighters exchanged punishing blows.
Rea, 27, landed power punches but the champion, 34, matched the intensity with effective uppercuts as the pace hardly diminished over twelve rounds.
The victor narrowly won the result with scoring tallies of 114-114, narrow lead and 115-112, but both fighters were determined and full of heart, exactly what their hero Hatton stood for.
