UK light heavyweight Buatsi made a winning yet disappointing debut to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a judges' verdict in a competitive 10-round fight at the Co-op Live Arena.
But Parker found success, delivering effective individual punches in a match where the techniques failed to mesh, with constant grabbing disrupting the action.
Two judges scored it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my best performance but how do champions respond? They succeed," Buatsi stated in the arena as he was greeted with negative reactions from the audience.
The Londoner got back to winning after his initial pro loss - an memorable fight with his previous opponent in last winter - to claim a twentieth professional win.
Various analysts thought the challenger, 31, should have been awarded the win but the British boxer experienced the second defeat of his 28-fight professional journey.
The Champion Claims Win in Uneventful Match
Buatsi's progress has plateaued in the past few years through promotional disputes and considerable time of inactivity.
Once tipped 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 fresh management.
He opened tentatively, with neither fighter prepared to be aggressive in a calculated initial rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was participating in his second fight at the higher weight class.
By the fight's midpoint, the underdog had stayed in contention, causing problems for the favorite, who worked behind a solid defense to edge the better periods.
The crowd's patience decreased during regular grabbing, with the challenger going down several times during close exchanges.
Parker closed well, but multiple periods were difficult to score. Nevertheless, ex-champion the boxing analyst - working with Dazn - had it particularly wide for the challenger, scoring for Buatsi just one round.
The victor progresses, but with the caliber of heavy hitter Benavidez, and Russian champion Bivol leading the category, the road to world glory - based on this performance - still seems difficult.
Ricky Hatton Memorial Motivates Local Rivalry Fight
In the secondary fight, Arthur overcame Bradley Rea by divided decision in a terrific local rivalry contest to secure the European light-heavyweight championship.
The arena fell silent for a deeply poignant homage prior to the bout as a bell ceremony sounded in memory of local hero Hatton, who died 46 years old in September.
It was the premier televised match card in the urban center since the passing of Hatton. As the last bell ended, the silence became a shout of "there's only one Ricky Hatton".
The fighting during the bout reflected the feeling. Arthur was floored by a significant blow flush on the chin in the second round, standing uncertainly to his position on the count of eight.
But the Manchester United-red attire of the fighter soon pressed ahead again. On the opposite side, Rea - in rival City blue - was injured quickly, heavy swelling appearing under his orbital area as the fighters traded punishing blows.
The challenger, twenty-seven, connected with strong blows but the champion, 34, matched the intensity with powerful upward punches as the action hardly diminished over twelve rounds.
The victor barely secured the decision with judges scorecards of 114-114, 115-113 and 115-112, but each competitor were determined and brave, exactly what their hero Hatton embodied.
