British light heavyweight Buatsi made a winning yet disappointing debut to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a judges' verdict in a close 10-round contest at the Manchester venue.
But Parker had his moments, connecting with powerful clean blows in a contest where the styles never quite clicked, with frequent clinching spoiling the contest.
Two judges scored it 96-94 to Buatsi, with the final judge a even score.
"It wasn't my greatest display but what do champions do? They succeed," the victor stated in the ring as he was greeted with boos from the crowd.
The Londoner returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in February - to claim a 20th career victory.
Some ringside observers felt the challenger, thirty-one, merited the decision but the Derbyshire fighter experienced the second defeat of his 28-fight career.
The Champion Secures Win in Slow Affair
Buatsi's progress has slowed in the past few years through management issues and extended periods of inactivity.
Once tipped as the next star of UK boxing, he now finds himself trying to realize his potential - maybe in what appears to be a last chance - under recent support.
He began cautiously, with neither fighter willing to take risks in a tentative early stages.
The challenger, whose sole prior loss 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 light heavyweight.
By the middle rounds, the underdog had stayed in contention, making life awkward for Buatsi, who utilized a protective stance to edge the cleaner stanzas.
The crowd's patience wore thin during regular grabbing, with Parker slipping to the canvas several times during close exchanges.
Parker ended stronger, but multiple periods were hard to judge. However, former world champion Carl Frampton - working with the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just one round.
The victor moves on, but with the caliber of hard hitter Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Hatton Memorial Fuels Manchester Derby Fight
In the co-main event, Lyndon Arthur beat Bradley Rea by split-decision in a excellent Manchester vs Manchester contest to win the European light-heavyweight championship.
The venue grew hushed for a profoundly moving tribute before the fight as 10 bells sounded in remembrance of Manchester's own Ricky Hatton, who passed away 46 years old in recently.
It was the first major televised boxing event in the urban center since Hatton's passing. As the concluding sound ended, the silence gave way to a chant of "there's only one Hatton".
The competition during the bout reflected the feeling. Arthur was knocked down by a left hook squarely on the chin in the initial stage, standing uncertainly to his footing on the referee's count.
But the red-colored attire of Arthur soon came forward again. On the opposite side, Rea - in opposing blue - was injured early, noticeable damage developing under his orbital area as the duo landed powerful shots.
The challenger, twenty-seven, delivered effective strikes but Arthur, thirty-four, responded in kind with stinging uppercuts as the action seldom decreased over 12 rounds.
The victor barely secured the verdict with official scores of draw, narrow lead and 115-112, but the two athletes were relentless and full of heart, everything their idol Hatton represented.
