UK light heavyweight Buatsi made a winning yet underwhelming start to his career under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a split decision in a tight 10-round contest at the Co-op Live Arena.
But Parker found success, connecting with powerful individual punches in a match where the techniques failed to mesh, with excessive holding spoiling the fight.
The scoring judges scored it 96-94 to Buatsi, with the third a 95-95 draw.
"It wasn't my finest showing but what defines champions? They win," Buatsi said in the arena as he was met by negative reactions from the audience.
The British fighter got back to winning after his initial pro loss - an thrilling contest with his previous opponent in last winter - to claim a 20th career victory.
Several boxing experts felt the challenger, 31, should have been awarded the victory but the British boxer suffered the second defeat of his 28-match career.
Buatsi Secures Triumph in Uneventful Encounter
His career development has stalled in the past few years through promotional disputes and long spells of lack of fights.
Earlier forecast as the future of the British fight scene, he now is positioned trying to realize his potential - perhaps in what appears to be a last chance - under recent support.
He began cautiously, with neither fighter ready to overcommit in a tentative 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 in the contest, was participating in his second fight at the higher weight class.
By the fight's midpoint, the underdog had kept it close, creating difficulties for Buatsi, who utilized a protective stance to barely take the cleaner periods.
The crowd's patience decreased because of constant clinching, with Parker going down several times during close exchanges.
The underdog closed well, but multiple periods were hard to judge. However, former world champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just one round.
Buatsi moves on, but with the likes of power puncher David Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - judging by this showing - still looks steep.
Ricky Hatton Homage Fuels Manchester Derby Fight
In the co-main event, Lyndon Arthur beat Rea by divided decision in a outstanding local rivalry contest to capture the European light-heavyweight title.
The venue fell silent for a deeply poignant tribute ahead of the contest as 10 bells sounded in honor of local hero Hatton, who died at age 46 in last month.
It was the premier televised fight night in the urban center since Hatton's death. As the last bell disappeared, the stillness gave way to a roar of "there's just one Ricky Hatton".
The action within the ring equaled the emotion. The eventual winner was knocked down by a significant blow squarely on the chin in the early round, rising shakily to his footing on the eight count.
But the Manchester United-red shorts of Arthur soon advanced again. Across the ring, the opponent - in rival City blue - was injured early, heavy swelling forming under his face as the duo exchanged hard punches.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, matched the intensity with powerful upward punches as the pace rarely dropped over the full distance.
Arthur barely secured the decision with scoring tallies of even score, 115-113 and 115-112, but each competitor were relentless and courageous, everything their hero Hatton stood for.
