British light heavyweight Buatsi made a winning yet disappointing beginning to his career under new promoters with a points victory over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a tight ten-round contest at the boxing arena.
But Parker landed significant shots, landing some telling single shots in a fight where the styles didn't complement each other, with excessive holding disrupting the fight.
The scoring judges had it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my finest performance but how do champions respond? They prevail," Buatsi stated in the arena as he was met by disapproval from the audience.
The British fighter got back to winning after his first professional defeat - an memorable fight with Callum Smith in last winter - to earn a 20th career victory.
Some ringside observers thought Parker, 31, deserved the decision but the British boxer suffered the second loss of his 28-match career.
Buatsi Claims Win in Uneventful Match
The fighter's advancement has plateaued in recent years through management issues and considerable time of inactivity.
Earlier forecast as the next star of British boxing, he now is positioned trying to realize his potential - possibly in what feels like a last chance - under recent support.
He opened tentatively, with both competitors prepared to be aggressive in a cagey initial rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second appearance at the higher weight class.
By the halfway stage, the underdog had kept it close, making life awkward for Buatsi, who operated with a tight guard to narrowly win the better periods.
The crowd's patience wore thin during regular grabbing, with Parker going down multiple occasions during grappling.
Parker ended stronger, but multiple periods were hard to judge. Nevertheless, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, giving Buatsi just one round.
The victor progresses, but with the caliber of power puncher David Benavidez, and Eastern European fighter Bivol dominating the weight class, the path to championship success - based on this performance - still seems difficult.
Hatton Homage Motivates Local Rivalry Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by close verdict in a excellent Manchester vs Manchester fight to secure the continental championship.
The arena became quiet for a profoundly moving homage before the fight as ten bells sounded in remembrance of Manchester's own Hatton, who passed away aged 46 in recently.
It was the premier televised fight night in the location since Hatton's passing. As the last bell ended, the silence gave way to a shout of "there's just one Ricky Hatton".
The competition inside the ropes reflected the sentiment. The eventual winner was sent to the canvas by a significant blow squarely on the face in the initial stage, standing uncertainly to his feet on the eight count.
But the Manchester United-red shorts of the fighter soon advanced again. From the other corner, Rea - in rival City blue - was injured soon, significant bruising developing under his eye as the duo traded powerful shots.
The challenger, twenty-seven, landed power punches but the champion, 34, responded in kind with powerful upward punches as the intensity rarely dropped over the full distance.
The victor narrowly won the decision with official scores of even score, close margin and clearer margin, but the two athletes were relentless and full of heart, exactly what their inspiration Hatton embodied.
