British light-heavyweight Buatsi made a winning yet unimpressive debut to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a split decision in a tight ten-round fight at the Co-op Live Arena.
But the challenger found success, landing some telling single shots in a contest where the styles didn't complement each other, with constant grabbing disrupting the fight.
Two judges scored it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my finest showing but what defines champions? They succeed," Buatsi commented in the ring as he was met by negative reactions from the audience.
The British fighter bounced back after his first professional defeat - an thrilling contest with his previous opponent in last winter - to secure a twentieth professional win.
Several boxing experts felt the challenger, thirty-one, should have been awarded the victory but the contender suffered the second defeat of his 28-bout professional journey.
Buatsi Earns Win in Dull Encounter
The fighter's advancement has slowed in recent times through management issues and extended periods of inactivity.
Previously predicted as the rising talent of the British fight scene, he now is positioned trying to fulfil that early promise - maybe in what seems like a last chance - under fresh management.
He began cautiously, with both competitors willing to be aggressive in a tentative early stages.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after damaging his hand mid-fight, was making just his second appearance at light heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for Buatsi, who utilized a protective stance to edge the cleaner periods.
The crowd's patience wore thin amid regular grabbing, with the challenger going down various instances during close exchanges.
Parker ended stronger, but several stanzas were difficult to score. However, former world champion Carl Frampton - working with Dazn - had it significantly in favor for Parker, awarding Buatsi just one round.
Buatsi advances, but with the likes of power puncher Benavidez, and Russian star Bivol leading the category, the road to world glory - based on this performance - still appears challenging.
Ricky Hatton Memorial Fuels Manchester Derby Battle
In the co-main event, Arthur overcame Rea by split-decision in a outstanding all-Manchester battle to capture the European light heavyweight belt.
The stadium grew hushed for a deeply poignant homage ahead of the contest as ten bells rang in remembrance of Manchester's own Hatton, who succumbed aged 46 in recently.
It was the premier televised fight night in the city since Hatton's passing. As the final chime faded, the quiet gave way to a chant of "there's only one Hatton".
The competition during the bout matched the feeling. The eventual winner was sent to the canvas by a powerful punch flush on the face in the second round, rising shakily to his footing on the referee's count.
But the Manchester United-red equipment of the fighter soon advanced again. Across the ring, Rea - in competitive blue - was damaged quickly, heavy swelling forming under his face as the fighters exchanged powerful shots.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, fought fire with fire with effective uppercuts as the pace hardly diminished over 12 rounds.
The victor narrowly won the result with judges scorecards of draw, 115-113 and wider gap, but the two athletes were relentless and brave, everything their inspiration the legend embodied.
