UK light-heavyweight Buatsi made a winning yet underwhelming start to his career under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a majority decision in a competitive ten-round contest at the Manchester venue.
But Parker found success, landing some telling clean blows in a fight where the approaches failed to mesh, with constant grabbing spoiling the contest.
Two judges had it 96-94 to the winner, with the third a 95-95 draw.
"It wasn't my greatest performance but how do champions respond? They succeed," the victor stated in the ringside as he was greeted with disapproval from the spectators.
The British fighter bounced back after his initial pro loss - an epic battle with Callum Smith in February - to claim a twentieth professional win.
Various analysts felt the challenger, 31, merited the victory but the contender suffered the second setback of his 28-match professional journey.
Buatsi Earns Victory in Slow Affair
His career development has slowed in the past few years through promotional disputes and long spells of inactivity.
Earlier forecast as the future of the British fight scene, he now finds himself trying to realize his potential - possibly in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with neither fighter prepared to overcommit in a calculated early stages.
Parker, whose single earlier setback came at super middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was competing in only his second fight at the higher weight class.
By the halfway stage, the underdog had made it competitive, creating difficulties for Buatsi, who operated with a protective stance to narrowly win the more effective periods.
The audience's tolerance decreased amid constant clinching, with the challenger going down several times during close exchanges.
The underdog closed well, but multiple periods were challenging to assess. Although, ex-champion Carl Frampton - commentating on the broadcast network - had it particularly wide for Parker, giving Buatsi just a single round.
Buatsi progresses, but with the presence of heavy hitter Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - judging by this showing - still looks steep.
Hatton Tribute Fuels All-Manchester Contest
In the secondary fight, Arthur defeated Bradley Rea by split-decision in a terrific all-Manchester contest to secure the continental belt.
The stadium became quiet for a extremely emotional homage ahead of the contest as 10 bells tolled in remembrance of the city's native Hatton, who succumbed 46 years old in recently.
It was the premier televised fight night in the location since Hatton's passing. As the concluding sound disappeared, the silence transitioned to a roar of "only one Hatton".
The competition inside the ropes reflected the sentiment. The eventual winner was knocked down by a significant blow squarely on the chin in the second round, standing uncertainly to his footing on the eight count.
But the Manchester United-red shorts of Arthur soon pressed ahead again. On the opposite side, Rea - in rival City blue - was injured soon, noticeable damage forming under his eye as the pair exchanged hard punches.
Rea, twenty-seven, connected with strong blows but the champion, 34, matched the intensity with stinging uppercuts as the pace hardly diminished over 12 rounds.
Arthur narrowly won the result with official scores of even score, narrow lead and 115-112, but each competitor were determined and brave, exactly what their hero the legend embodied.
