UK light heavyweight Buatsi earned a win yet unimpressive start to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a split 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 frequent clinching spoiling the fight.
Two judges had it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my best showing but what do champions do? They succeed," Buatsi said in the arena as he was greeted with boos from the audience.
The Londoner bounced back after his maiden career setback - an epic battle with Callum Smith in last winter - to claim a twentieth professional win.
Several boxing experts felt the challenger, thirty-one, deserved the decision but the Derbyshire fighter experienced the second loss of his 28-bout professional journey.
The Champion Secures Win in Uneventful Match
His career development has stalled in recent times through contract problems and considerable time of lack of fights.
Earlier forecast as the future of the British fight scene, he now finds himself trying to fulfil that early promise - possibly in what feels like a ultimate opportunity - under recent support.
He began cautiously, with neither fighter ready to overcommit in a cagey opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after breaking his hand in the contest, was competing in only his second fight at light-heavyweight.
By the fight's midpoint, the underdog had stayed in contention, making life awkward for the favorite, who worked behind a tight guard to narrowly win the cleaner stanzas.
The audience's tolerance wore thin because of regular grabbing, with Parker slipping to the canvas various instances during clinches.
Parker closed well, but several stanzas were difficult to score. Although, ex-champion the boxing analyst - providing analysis for Dazn - had it strongly leaning for the challenger, awarding Buatsi just one round.
The victor moves on, but with the likes of power puncher David Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - on this evidence - still seems difficult.
Ricky Hatton Tribute Inspires All-Manchester Contest
In the co-main event, Arthur beat Bradley Rea by divided decision in a outstanding Manchester vs Manchester battle to secure the European light heavyweight championship.
The stadium fell silent for a extremely emotional memorial prior to the bout as a bell ceremony tolled in remembrance of the city's native Hatton, who succumbed at age 46 in September.
It was the premier televised boxing event in the urban center since the passing of Hatton. As the concluding sound ended, the stillness became a shout of "there's only one Ricky Hatton".
The action inside the ropes reflected the feeling. Arthur was sent to the canvas by a left hook squarely on the face in the second round, rising shakily to his footing on the referee's count.
But the Manchester United-red attire of Arthur soon pressed ahead again. On the opposite side, Rea - in rival City blue - was damaged soon, heavy swelling developing under his eye as the duo traded powerful shots.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the action hardly diminished over twelve rounds.
Arthur narrowly won the decision with official scores of even score, close margin and 115-112, but the two athletes were persistent and full of heart, everything their idol Hatton stood for.
