British light heavyweight Buatsi earned a win yet unimpressive beginning to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a judges' verdict in a tight ten-round contest at the Co-op Live Arena.
But the challenger landed significant shots, delivering effective individual punches in a fight where the techniques didn't complement each other, with constant grabbing marring the action.
The officials judged it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest showing but what do champions do? They succeed," the victor commented in the arena as he was faced boos from the spectators.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers felt the challenger, thirty-one, should have been awarded the win but the Derbyshire fighter suffered the second loss of his 28-bout career.
Buatsi Earns Victory in Dull Encounter
Buatsi's progress has plateaued in recent times through promotional disputes and extended periods of lack of fights.
Earlier forecast as the future of UK boxing, he now stands trying to achieve expectations - possibly in what seems like a ultimate opportunity - under fresh management.
He opened tentatively, with both competitors ready to take risks in a cagey initial rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after breaking his hand during the bout, was making just his second bout at light-heavyweight.
By the halfway stage, Parker had kept it close, making life awkward for Buatsi, who operated with a solid defense to edge the more effective rounds.
The spectators' acceptance wore thin during frequent holding, with the challenger going down several times during close exchanges.
Parker ended stronger, but many rounds were hard to judge. However, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, giving Buatsi just only one stanza.
The victor moves on, but with the presence of hard hitter David Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - on this evidence - still seems difficult.
Ricky Hatton Homage Inspires Local Rivalry Battle
In the co-main event, Lyndon Arthur beat Rea by close verdict in a outstanding Manchester vs Manchester fight to secure the European light-heavyweight title.
The stadium became quiet for a deeply poignant memorial prior to the bout as a bell ceremony tolled in honor of the city's native Hatton, who succumbed aged 46 in last month.
It was the premier televised boxing event in the urban center since Hatton's death. As the concluding sound ended, the silence transitioned to a shout of "only one Hatton".
The fighting within the ring equaled the feeling. Arthur was floored by a significant blow directly to the face in the initial stage, standing uncertainly to his footing on the count of eight.
But the traditional red equipment of Arthur soon advanced again. From the other corner, the opponent - in rival City blue - was marked up soon, heavy swelling appearing under his orbital area as the fighters traded punishing blows.
The challenger, 27, connected with strong blows but Arthur, thirty-four, fought fire with fire with powerful upward punches as the action rarely dropped over the full distance.
Arthur barely secured the verdict with scoring tallies of draw, 115-113 and wider gap, but both fighters were determined and courageous, exactly what their idol Hatton embodied.
