UK light-heavyweight Buatsi made a winning yet disappointing debut to his career under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a majority decision in a tight 10-round fight at the boxing arena.
But Parker had his moments, delivering effective clean blows in a contest where the techniques failed to mesh, with frequent clinching spoiling the contest.
The officials had it 96-94 for to the winner, with the third a even score.
"It wasn't my greatest display but how do champions respond? They prevail," Buatsi stated in the ring as he was faced boos from the crowd.
The British fighter bounced back after his first professional defeat - an memorable fight with Callum Smith in February - to earn a twentieth professional win.
Some ringside observers thought Parker, thirty-one, merited the decision but the British boxer suffered the second defeat of his 28-bout career.
Buatsi Secures Triumph in Uneventful Encounter
His career development has stalled in recent years through management issues and extended periods of lack of fights.
Previously predicted as the rising talent of British boxing, he now is positioned trying to realize his potential - possibly in what appears to be a ultimate opportunity - under fresh management.
He started carefully, with neither fighter ready to take risks in a tentative initial rounds.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was participating in his second bout at the higher weight class.
By the middle rounds, the underdog had kept it close, creating difficulties for the favorite, who worked behind a solid defense to narrowly win the cleaner stanzas.
The crowd's patience decreased because of constant clinching, with the challenger falling to the floor multiple occasions during grappling.
Parker closed well, but multiple periods were challenging to assess. Although, ex-champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for the challenger, awarding Buatsi just one round.
Buatsi advances, but with the presence of power puncher David Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - based on this performance - still seems difficult.
Hatton Memorial Motivates Local Rivalry Battle
In the co-main event, Lyndon Arthur defeated Rea by close verdict in a outstanding local rivalry fight to secure the European light heavyweight title.
The arena fell silent for a extremely emotional tribute before the fight as ten bells tolled in honor of local hero Hatton, who succumbed aged 46 in recently.
It was the premier televised fight night in the urban center since the passing of Hatton. As the concluding sound faded, the stillness gave way to a shout of "there's just one Hatton".
The action during the bout matched the sentiment. Arthur was floored by a significant blow squarely on the face in the early round, standing uncertainly to his footing on the eight count.
But the red-colored shorts of the fighter soon came forward again. On the opposite side, the opponent - in competitive blue - was damaged early, noticeable damage appearing under his face as the fighters landed hard punches.
The challenger, 27, connected with strong blows but the champion, thirty-four, responded in kind with effective uppercuts as the pace rarely dropped over twelve rounds.
Arthur narrowly won the result with scoring tallies of even score, close margin and 115-112, but each competitor were determined and full of heart, exactly what their idol the legend embodied.
