UK light-heavyweight Buatsi secured a victory yet unimpressive beginning to his career under recent management with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a judges' verdict in a competitive ten-round fight at the boxing arena.
But Parker found success, connecting with powerful single shots in a match where the techniques didn't complement each other, with constant grabbing spoiling the fight.
The scoring judges scored it 96-94 to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest display but what defines champions? They succeed," Buatsi said in the arena as he was greeted with negative reactions from the spectators.
The British fighter got back to winning after his first professional defeat - an thrilling contest with his previous opponent in last winter - to earn a 20th career victory.
Several boxing experts thought Parker, thirty-one, merited the decision but the Derbyshire fighter endured the second setback of his 28-match career.
The Champion Claims Victory in Uneventful Encounter
The fighter's advancement has slowed in the past few years through management issues and long spells of lack of fights.
Once tipped as the next star of British boxing, he now is positioned trying to fulfil that early promise - maybe in what feels like a last chance - under recent support.
He opened tentatively, with neither fighter ready to overcommit in a cagey opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in two years ago after damaging his hand during the bout, was competing in only his second bout at the higher weight class.
By the middle rounds, the underdog had kept it close, causing problems for the favorite, who worked behind a solid defense to barely take the better periods.
The crowd's patience decreased because of constant clinching, with Parker going down various instances during close exchanges.
The underdog finished the stronger, but multiple periods were difficult to score. Nevertheless, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, scoring for Buatsi just a single round.
The victor progresses, but with the presence of hard hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Memorial Inspires Manchester Derby Battle
In the co-main event, Lyndon Arthur overcame Bradley Rea by split-decision in a terrific local rivalry fight to win the European light heavyweight title.
The stadium fell silent for a profoundly moving memorial prior to the bout as 10 bells sounded in honor of local hero Hatton, who succumbed at age 46 in recently.
It was the premier televised fight night in the location since Hatton's death. As the last bell faded, the quiet became a roar of "only one Hatton".
The fighting inside the ropes matched the sentiment. Arthur was sent to the canvas by a significant blow directly to the jaw in the early round, rising shakily to his footing on the count of eight.
But the Manchester United-red shorts of the fighter soon advanced again. Across the ring, Rea - in rival City blue - was marked up early, noticeable damage forming under his orbital area as the fighters landed hard punches.
Rea, 27, delivered effective strikes but the champion, 34, matched the intensity with stinging uppercuts as the intensity hardly diminished over twelve rounds.
Arthur edged the decision with official scores of 114-114, narrow lead and clearer margin, but the two athletes were relentless and full of heart, everything their idol the legend stood for.
