British light-heavyweight Buatsi secured a victory yet disappointing beginning to life under recent management with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a majority decision in a competitive 10-round contest at the Manchester venue.
But the challenger landed significant shots, landing some telling clean blows in a fight where the approaches failed to mesh, with excessive holding disrupting the action.
The officials had it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my greatest performance but how do champions respond? They prevail," the victor commented in the arena as he was faced negative reactions from the spectators.
The Londoner got back to winning after his first professional defeat - an memorable fight with his previous opponent in February - to claim a 20th pro success.
Some ringside observers thought the challenger, 31, deserved the win but the British boxer suffered the second defeat of his 28-match career.
The Champion Secures Win in Slow Encounter
Buatsi's progress has slowed in recent times through contract problems and long spells of inactivity.
Once tipped as the future of UK boxing, he now finds himself trying to achieve expectations - possibly in what seems like a ultimate opportunity - under fresh management.
He opened tentatively, with the two boxers willing to take risks in a calculated early stages.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in two years ago after breaking his hand mid-fight, was participating in his second bout at light heavyweight.
By the middle rounds, Parker had made it competitive, creating difficulties for the favorite, who utilized a tight guard to edge the more effective periods.
The audience's tolerance wore thin during constant clinching, with Parker falling to the floor several times during close exchanges.
Parker ended stronger, but several stanzas were challenging to assess. However, ex-champion the boxing analyst - working with Dazn - had it significantly in favor for Parker, scoring for Buatsi just a single round.
The victor progresses, but with the likes of power puncher David Benavidez, and Eastern European fighter Bivol leading the category, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Homage Fuels Manchester Derby Battle
In the co-main event, Lyndon Arthur beat Bradley Rea by split-decision in a excellent Manchester vs Manchester battle to secure the European light heavyweight title.
The stadium fell silent for a deeply poignant homage prior to the bout as 10 bells rang in remembrance of local hero Ricky Hatton, who succumbed aged 46 in September.
It was the premier televised fight night in the city since Hatton's passing. As the concluding sound faded, the silence transitioned to a roar of "there's just one Ricky Hatton".
The competition within the ring matched the feeling. The eventual winner was knocked down by a left hook squarely on the jaw in the initial stage, rising shakily to his footing on the eight count.
But the Manchester United-red shorts of the fighter soon advanced again. On the opposite side, Rea - in opposing blue - was injured soon, noticeable damage appearing under his face as the duo traded powerful shots.
Rea, 27, landed power punches but Arthur, thirty-four, fought fire with fire with powerful upward punches as the pace seldom decreased over 12 rounds.
Arthur barely secured the result with scoring tallies of 114-114, 115-113 and wider gap, but both fighters were persistent and full of heart, exactly what their hero Hatton embodied.
