UK light-heavyweight Buatsi made a winning yet underwhelming start to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a split decision in a tight ten-round bout at the boxing arena.
But Parker found success, delivering effective individual punches in a match where the styles never quite clicked, with frequent clinching marring the contest.
The officials scored it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest display but what do champions do? They succeed," Buatsi stated in the ringside as he was met by negative reactions from the audience.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in last winter - to secure a 20th career victory.
Several boxing experts thought Parker, 31, should have been awarded the decision but the Derbyshire fighter suffered the second loss of his 28-fight professional journey.
Buatsi Earns Win in Uneventful Affair
The fighter's advancement has plateaued in recent times through management issues and considerable time of inactivity.
Once tipped as the future of UK boxing, he now finds himself trying to achieve expectations - maybe in what seems like a ultimate opportunity - under fresh management.
He began cautiously, with the two boxers prepared to be aggressive in a calculated opening few rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in two years ago after damaging his hand mid-fight, was making just his second bout at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, creating difficulties for Buatsi, who operated with a solid defense to edge the cleaner rounds.
The spectators' acceptance wore thin during constant clinching, with the challenger falling to the floor various instances during grappling.
Parker ended stronger, but several stanzas were challenging to assess. However, former world champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for Parker, giving Buatsi just a single round.
The victor advances, but with the likes of hard hitter Benavidez, and Russian star Bivol dominating the weight class, the path to championship success - on this evidence - still appears challenging.
Hatton Memorial Inspires Manchester Derby Fight
In the co-main event, Arthur beat Bradley Rea by divided decision in a outstanding all-Manchester battle to capture the continental title.
The venue fell silent for a deeply poignant tribute ahead of the contest as a bell ceremony sounded in memory of Manchester's own Ricky Hatton, who passed away 46 years old in last month.
It was the first major televised match card in the urban center since Hatton's death. As the last bell ended, the silence transitioned to a shout of "there's only one Ricky Hatton".
The action during the bout matched the sentiment. The eventual winner was knocked down by a powerful punch directly to the jaw in the initial stage, getting up unsteadily to his position on the count of eight.
But the traditional red shorts of Arthur soon pressed ahead again. On the opposite side, Rea - in rival City blue - was injured early, significant bruising appearing under his face as the pair traded hard punches.
The challenger, 27, landed power punches but the champion, thirty-four, responded in kind with stinging uppercuts as the action hardly diminished over 12 rounds.
The victor edged the decision with scoring tallies of even score, close margin and clearer margin, but both fighters were persistent and full of heart, exactly what their idol Hatton represented.
