UK light heavyweight Buatsi made a winning yet unimpressive start to his career under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a judges' verdict in a close ten-round contest at the Manchester venue.
But the challenger had his moments, connecting with powerful clean blows in a contest where the approaches failed to mesh, with constant grabbing marring the action.
Two judges judged it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my greatest showing but what defines champions? They prevail," Buatsi stated in the ring as he was faced negative reactions from the audience.
The Londoner bounced back after his initial pro loss - an memorable fight with Callum Smith in February - to claim a 20th career victory.
Some ringside observers felt Parker, thirty-one, merited the victory but the Derbyshire fighter experienced the second defeat of his 28-match professional journey.
The Champion Earns Win in Dull Encounter
Buatsi's progress has slowed in recent times through promotional disputes and long spells of inactivity.
Once tipped as the next star of British boxing, he now finds himself trying to achieve expectations - maybe in what appears to be a last chance - under fresh management.
He began cautiously, with both competitors willing to be aggressive in a calculated initial rounds.
Parker, whose only previous defeat came at super-middleweight against John Ryder in 2022 after breaking his hand in the contest, was participating in his second bout at the higher weight class.
By the fight's midpoint, the underdog had kept it close, causing problems for Buatsi, who worked behind a solid defense to edge the cleaner periods.
The audience's tolerance wore thin amid frequent holding, with the challenger going down several times during grappling.
The underdog ended stronger, but several stanzas were challenging to assess. Although, previous titleholder Carl Frampton - providing analysis for Dazn - had it significantly in favor for the challenger, awarding Buatsi just only one stanza.
The victor advances, but with the presence of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the road to world glory - judging by this showing - still looks steep.
Ricky Hatton Tribute Motivates Local Rivalry Fight
In the supporting bout, Lyndon Arthur beat Bradley Rea by close verdict in a excellent all-Manchester battle to win the continental title.
The arena fell silent for a deeply poignant homage prior to the bout as a bell ceremony tolled in honor of the city's native Ricky Hatton, who succumbed at age 46 in last month.
It was the premier televised boxing event in the location since Hatton's passing. As the last bell faded, the silence transitioned to a roar of "there's only one Ricky Hatton".
The fighting during the bout matched the feeling. The eventual winner was floored by a significant blow directly to the jaw in the second round, standing uncertainly to his footing on the referee's count.
But the red-colored shorts of Arthur soon pressed ahead again. On the opposite side, Rea - in competitive blue - was damaged soon, heavy swelling developing under his eye as the fighters landed hard punches.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, responded in kind with stinging uppercuts as the pace hardly diminished over twelve rounds.
The victor barely secured the decision with official scores of 114-114, 115-113 and clearer margin, but each competitor were determined and courageous, everything their hero Hatton represented.
