British light heavyweight Buatsi earned a win yet underwhelming start to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a close 10-round bout at the boxing arena.
But the challenger landed significant shots, landing some telling individual punches in a contest where the styles never quite clicked, with constant grabbing spoiling the action.
Two judges had it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my best performance but what defines champions? They win," Buatsi commented in the arena as he was met by disapproval from the spectators.
The Londoner bounced back after his first professional defeat - an memorable fight with Callum Smith in February - to claim a twentieth professional win.
Some ringside observers thought Parker, thirty-one, should have been awarded the decision but the Derbyshire fighter experienced the second setback of his 28-bout career.
Buatsi Secures Win in Dull Affair
The fighter's advancement has slowed in recent years through management issues and considerable time of inactivity.
Previously predicted as the next star of the British fight scene, he now is positioned trying to achieve expectations - perhaps in what appears to be a ultimate opportunity - under fresh management.
He started carefully, with neither fighter willing to take risks in a tentative early stages.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in two years ago after damaging his hand during the bout, was participating in his second fight at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for Buatsi, who operated with a solid defense to barely take the cleaner periods.
The audience's tolerance diminished during constant clinching, with Parker going down several times during grappling.
Parker closed well, but many rounds were challenging to assess. However, ex-champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, giving Buatsi just only one stanza.
The victor advances, but with the caliber of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Tribute Motivates Local Rivalry Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by split-decision in a terrific local rivalry contest to win the European light-heavyweight title.
The stadium fell silent for a profoundly moving homage before the fight as 10 bells rang in remembrance of Manchester's own Hatton, who passed away aged 46 in September.
It was the initial significant broadcast match card in the urban center since Hatton's passing. As the final chime ended, the stillness gave way to a chant of "only one Ricky Hatton".
The fighting during the bout reflected the sentiment. Arthur was knocked down by a left hook flush on the chin in the early round, standing uncertainly to his feet on the eight count.
But the Manchester United-red attire of Arthur soon pressed ahead again. From the other corner, the opponent - in opposing blue - was marked up early, heavy swelling developing under his eye as the fighters exchanged powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with powerful upward punches as the action rarely dropped over 12 rounds.
Arthur edged the result with judges scorecards of 114-114, close margin and clearer margin, but both fighters were relentless and full of heart, everything their inspiration Hatton represented.
