British light heavyweight Buatsi made a winning yet underwhelming beginning to his career under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a judges' verdict in a competitive 10-round fight at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling single shots in a fight where the approaches never quite clicked, with constant grabbing marring the action.
The scoring judges had it 96-94 to Buatsi, with the remaining official a even score.
"It wasn't my greatest performance but how do champions respond? They win," Buatsi commented in the ringside as he was faced negative reactions from the audience.
The British fighter bounced back after his first professional defeat - an memorable fight with Callum Smith in last winter - to secure a twentieth professional win.
Various analysts felt the challenger, 31, should have been awarded the win but the Derbyshire fighter experienced the second loss of his 28-match career.
The Champion Earns Triumph in Slow Match
The fighter's advancement has stalled in recent years through management issues and considerable time of lack of fights.
Once tipped as the next star of British boxing, he now is positioned trying to realize his potential - perhaps in what appears to be a ultimate opportunity - under recent support.
He started carefully, with neither fighter prepared to take risks in a calculated initial rounds.
Parker, whose single earlier setback came at super-middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was competing in only his second bout at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, making life awkward for Buatsi, who utilized a solid defense to narrowly win the better periods.
The spectators' acceptance diminished because of constant clinching, with Parker going down several times during clinches.
Parker finished the stronger, but many rounds were challenging to assess. However, ex-champion the boxing analyst - working with Dazn - had it strongly leaning for Parker, giving Buatsi just only one stanza.
Buatsi moves on, but with the caliber of heavy hitter David Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Tribute Inspires Local Rivalry Contest
In the co-main event, Lyndon Arthur beat Bradley Rea by split-decision in a excellent local rivalry fight to secure the European light-heavyweight championship.
The venue grew hushed for a extremely emotional homage prior to the bout as a bell ceremony tolled in remembrance of local hero Ricky Hatton, who died 46 years old in recently.
It was the premier televised fight night in the location since Hatton's death. As the last bell faded, the stillness transitioned to a chant of "there's only one Hatton".
The competition within the ring reflected the sentiment. The eventual winner was knocked down by a powerful punch squarely on the jaw in the second round, rising shakily to his position on the count of eight.
But the Manchester United-red equipment of Arthur soon came forward again. From the other corner, Rea - in opposing blue - was damaged soon, heavy swelling forming under his face as the pair exchanged punishing blows.
Rea, twenty-seven, landed power punches but Arthur, 34, responded in kind with stinging uppercuts as the intensity hardly diminished over the full distance.
The victor edged the verdict with scoring tallies of draw, 115-113 and wider gap, but the two athletes were determined and full of heart, exactly what their inspiration the legend represented.
