British light heavyweight Buatsi earned a win yet underwhelming start to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a judges' verdict in a competitive 10-round contest at the Manchester venue.
But Parker landed significant shots, connecting with powerful clean blows in a match where the styles never quite clicked, with excessive holding marring the action.
The officials scored it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my best display but what defines champions? They succeed," the victor said in the ringside as he was met by boos from the spectators.
The Londoner bounced back after his initial pro loss - an thrilling contest with Callum Smith in February - to secure a 20th career victory.
Some ringside observers believed the challenger, thirty-one, should have been awarded the victory but the Derbyshire fighter endured the second loss of his 28-match career.
The Champion Claims Triumph in Slow Encounter
The fighter's advancement has stalled in the past few years through management issues and considerable time of inactivity.
Once tipped as the future of the British fight scene, he now is positioned trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under recent support.
He started carefully, with the two boxers ready to be aggressive in a calculated initial rounds.
Parker, whose only previous defeat came at the lower weight class against his former opponent in two years ago after suffering a hand injury mid-fight, was making just his second appearance at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, causing problems for Buatsi, who worked behind a tight guard to narrowly win the cleaner stanzas.
The spectators' acceptance diminished because of constant clinching, with the challenger going down several times during clinches.
The underdog finished the stronger, but several stanzas were challenging to assess. However, ex-champion the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
The victor advances, but with the caliber of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - based on this performance - still appears challenging.
Hatton Homage Fuels All-Manchester Fight
In the secondary fight, Arthur overcame Bradley Rea by split-decision in a outstanding local rivalry battle to secure the European light-heavyweight championship.
The arena fell silent for a extremely emotional tribute prior to the bout as ten bells sounded in memory of the city's native Ricky Hatton, who died 46 years old in recently.
It was the first major televised fight night in the location since Hatton's passing. As the final chime faded, the silence transitioned to a chant of "there's just one Ricky Hatton".
The action during the bout equaled the feeling. Arthur was floored by a powerful punch flush on the chin in the early round, standing uncertainly to his footing on the count of eight.
But the Manchester United-red attire of Arthur soon advanced again. From the other corner, the opponent - in competitive blue - was damaged soon, heavy swelling appearing under his eye as the pair exchanged powerful shots.
The challenger, 27, connected with strong blows but the champion, 34, responded in kind with powerful upward punches as the action seldom decreased over 12 rounds.
Arthur narrowly won the decision with scoring tallies of draw, 115-113 and 115-112, but each competitor were relentless and brave, exactly what their hero the legend embodied.
