UK light-heavyweight Buatsi made a winning yet disappointing debut to life under recent management with a unanimous decision over Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a majority decision in a close 10-round contest at the Co-op Live Arena.
But the challenger had his moments, connecting with powerful clean blows in a match where the styles didn't complement each other, with excessive holding disrupting the contest.
Two judges judged it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my best showing but what defines champions? They win," the victor stated in the ringside as he was greeted with disapproval from the crowd.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in February - to secure a 20th pro success.
Several boxing experts believed the challenger, 31, merited the victory but the British boxer experienced the second loss of his 28-match professional journey.
Buatsi Claims Victory in Dull Match
Buatsi's progress has stalled in recent years through contract problems and extended periods of lack of fights.
Earlier forecast as the future of UK boxing, he now is positioned trying to fulfil that early promise - perhaps in what feels like a ultimate opportunity - under fresh management.
He began cautiously, with both competitors prepared to be aggressive in a tentative opening few rounds.
Parker, whose single earlier setback came at super middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was participating in his second appearance at light-heavyweight.
By the middle rounds, Parker had kept it close, making life awkward for Buatsi, who operated with a tight guard to edge the better stanzas.
The spectators' acceptance decreased during frequent holding, with Parker falling to the floor multiple occasions during clinches.
The underdog ended stronger, but multiple periods were hard to judge. However, previous titleholder the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi advances, but with the likes of power puncher David Benavidez, and Russian champion Bivol leading the category, the journey to titles - on this evidence - still appears challenging.
Hatton Memorial Fuels Local Rivalry Contest
In the co-main event, Lyndon Arthur defeated Bradley Rea by close verdict in a excellent Manchester vs Manchester battle to secure the European light-heavyweight title.
The stadium became quiet for a deeply poignant homage ahead of the contest as ten bells sounded in memory of local hero Hatton, who passed away 46 years old in recently.
It was the premier televised fight night in the location since Hatton's passing. As the last bell disappeared, the silence gave way to a roar of "only one Ricky Hatton".
The action inside the ropes matched the feeling. The eventual winner was floored by a left hook flush on the chin in the early round, standing uncertainly to his position on the count of eight.
But the traditional red shorts of the fighter soon pressed ahead again. From the other corner, Rea - in rival City blue - was damaged soon, significant bruising developing under his face as the fighters traded punishing blows.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, fought fire with fire with powerful upward punches as the action rarely dropped over twelve rounds.
The victor narrowly won the decision with scoring tallies of 114-114, narrow lead and 115-112, but both fighters were relentless and full of heart, exactly what their idol the legend represented.
