British light heavyweight Buatsi secured a victory yet disappointing debut to his career under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a judges' verdict in a tight ten-round contest at the Co-op Live Arena.
But the challenger had his moments, landing some telling single shots in a contest where the approaches never quite clicked, with excessive holding marring the contest.
The scoring judges had it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest performance but what defines champions? They win," the victor said in the arena as he was greeted with negative reactions from the spectators.
The British fighter bounced back after his maiden career setback - an memorable fight with Callum Smith in last winter - to secure a twentieth professional win.
Several boxing experts felt Parker, thirty-one, deserved the decision but the Derbyshire fighter experienced the second loss of his 28-bout professional journey.
Buatsi Earns Victory in Dull Affair
Buatsi's progress has plateaued in recent times through management issues and considerable time of inactivity.
Earlier forecast as the future of the British fight scene, he now stands trying to achieve expectations - maybe in what feels like a ultimate opportunity - under recent support.
He started carefully, with the two boxers ready to take risks in a tentative opening few rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second fight at light-heavyweight.
By the halfway stage, Parker had stayed in contention, making life awkward for Buatsi, who worked behind a tight guard to edge the more effective periods.
The audience's tolerance decreased amid regular grabbing, with the challenger going down several times during grappling.
The underdog finished the stronger, but multiple periods were difficult to score. Nevertheless, former world champion Carl Frampton - commentating on the broadcast network - had it significantly in favor for Parker, awarding Buatsi just only one stanza.
The victor moves on, but with the presence of heavy hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - based on this performance - still appears challenging.
Hatton Memorial Fuels All-Manchester Contest
In the secondary fight, Arthur defeated Rea by divided decision in a excellent local rivalry contest to capture the European light-heavyweight belt.
The arena became quiet for a extremely emotional homage prior to the bout as a bell ceremony tolled in remembrance of Manchester's own Hatton, who passed away aged 46 in recently.
It was the first major televised fight night in the urban center since Hatton's death. As the last bell disappeared, the silence transitioned to a roar of "there's only one Ricky Hatton".
The fighting during the bout reflected the feeling. Arthur was floored by a significant blow squarely on the chin in the initial stage, rising shakily to his position on the referee's count.
But the red-colored attire of Arthur soon advanced again. On the opposite side, Rea - in rival City blue - was marked up quickly, significant bruising forming under his eye as the fighters landed powerful shots.
Rea, twenty-seven, connected with strong blows but Arthur, 34, fought fire with fire with effective uppercuts as the pace rarely dropped over 12 rounds.
The victor barely secured the result with judges scorecards of draw, close margin and 115-112, but the two athletes were determined and full of heart, all the qualities their inspiration the legend stood for.
