British light heavyweight Buatsi earned a win yet unimpressive start to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a tight ten-round contest at the boxing arena.
But Parker had his moments, connecting with powerful individual punches in a match where the approaches failed to mesh, with frequent clinching disrupting the action.
The officials had it 96-94 for to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my finest display but what defines champions? They win," the victor stated in the ring as he was greeted with negative reactions from the crowd.
The British fighter bounced back after his first professional defeat - an thrilling contest with his previous opponent in February - to claim a 20th pro success.
Various analysts believed the challenger, thirty-one, should have been awarded the victory but the Derbyshire fighter suffered the second defeat of his 28-fight career.
Buatsi Earns Victory in Uneventful Affair
His career development has stalled in the past few years through contract problems and extended periods of lack of fights.
Once tipped as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - possibly in what feels like a last chance - under recent support.
He started carefully, with the two boxers willing to take risks in a tentative early stages.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after breaking his hand mid-fight, was making just his second appearance at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for the favorite, who utilized a solid defense to edge the more effective periods.
The crowd's patience decreased during constant clinching, with the challenger falling to the floor various instances during close exchanges.
The underdog ended stronger, but several stanzas were challenging to assess. However, previous titleholder Carl Frampton - commentating on Dazn - had it strongly leaning for Parker, giving Buatsi just only one stanza.
Buatsi moves on, but with the presence of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - judging by this showing - still seems difficult.
Hatton Homage Motivates All-Manchester Contest
In the secondary fight, Arthur overcame Rea by divided decision in a outstanding local rivalry fight to win the European light heavyweight championship.
The arena fell silent for a extremely emotional homage prior to the bout as ten bells tolled in honor of local hero Ricky Hatton, who succumbed 46 years old in September.
It was the premier televised fight night in the city since Hatton's passing. As the last bell disappeared, the silence transitioned to a roar of "there's just one Ricky Hatton".
The fighting during the bout matched the feeling. Arthur was knocked down by a significant blow flush on the face in the initial stage, standing uncertainly to his position on the count of eight.
But the traditional red shorts of Arthur soon advanced again. Across the ring, the opponent - in opposing blue - was injured soon, heavy swelling developing under his eye as the fighters exchanged hard punches.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with powerful upward punches as the pace seldom decreased over 12 rounds.
Arthur narrowly won the verdict with official scores of 114-114, close margin and clearer margin, but each competitor were persistent and full of heart, all the qualities their hero Hatton embodied.
