British light-heavyweight Buatsi secured a victory yet unimpressive start to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a split decision in a competitive ten-round bout at the Manchester venue.
But Parker found success, connecting with powerful clean blows in a contest where the approaches didn't complement each other, with frequent clinching spoiling the fight.
The scoring judges scored it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my best performance but what do champions do? They win," the victor commented in the arena as he was faced disapproval from the spectators.
The British fighter bounced back after his initial pro loss - an thrilling contest with Callum Smith in last winter - to secure a 20th pro success.
Various analysts felt the challenger, 31, deserved the decision but the British boxer endured the second defeat of his 28-fight career.
The Champion Secures Triumph in Slow Match
Buatsi's progress has plateaued in recent times through promotional disputes and extended periods of lack of fights.
Previously predicted as the next star of UK boxing, he now is positioned trying to fulfil that early promise - maybe in what feels like a last chance - under recent support.
He started carefully, with both competitors prepared to be aggressive in a tentative early stages.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after suffering a hand injury in the contest, was competing in only his second bout at light heavyweight.
By the middle rounds, the underdog had made it competitive, causing problems for the favorite, who utilized a solid defense to narrowly win the more effective stanzas.
The audience's tolerance diminished amid constant clinching, with Parker slipping to the canvas multiple occasions during close exchanges.
The underdog finished the stronger, but multiple periods were hard to judge. Although, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just only one stanza.
The victor moves on, but with the caliber of heavy hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still looks steep.
Hatton Tribute Inspires Local Rivalry Fight
In the secondary fight, Arthur beat Bradley Rea by split-decision in a excellent all-Manchester contest to capture the European light heavyweight belt.
The stadium grew hushed for a deeply poignant tribute prior to the bout as 10 bells sounded in remembrance of local hero Hatton, who died at age 46 in recently.
It was the premier televised boxing event in the city since Hatton's death. As the final chime disappeared, the stillness transitioned to a roar of "only one Ricky Hatton".
The action during the bout equaled the feeling. Arthur was floored by a significant blow squarely on the face in the initial stage, getting up unsteadily to his feet on the eight count.
But the traditional red attire of the fighter soon advanced again. From the other corner, the opponent - in competitive blue - was injured quickly, heavy swelling appearing under his eye as the fighters traded hard punches.
Rea, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the action rarely dropped over twelve rounds.
The victor barely secured the result with scoring tallies of 114-114, close margin and 115-112, but both fighters were persistent and full of heart, all the qualities their hero the legend embodied.
