British light heavyweight Buatsi made a winning yet underwhelming start to his career under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a majority decision in a close 10-round contest at the boxing arena.
But Parker landed significant shots, delivering effective individual punches in a fight where the approaches failed to mesh, with excessive holding disrupting the fight.
Two judges had it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my best performance but what do champions do? They win," Buatsi stated in the ringside as he was faced negative reactions from the spectators.
The Londoner got back to winning after his first professional defeat - an memorable fight with Callum Smith in February - to earn a 20th pro success.
Various analysts thought the challenger, thirty-one, should have been awarded the victory but the contender endured the second defeat of his 28-bout career.
The Champion Earns Victory in Dull Encounter
The fighter's advancement has plateaued in recent years through management issues and considerable time of inactivity.
Earlier forecast as the next star of UK boxing, he now stands trying to achieve expectations - possibly in what seems like a last chance - under recent support.
He started carefully, with the two boxers prepared to take risks in a tentative opening few rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was participating in his second fight at the higher weight class.
By the middle rounds, the underdog had kept it close, creating difficulties for Buatsi, who worked behind a protective stance to barely take the more effective periods.
The audience's tolerance diminished amid frequent holding, with the challenger slipping to the canvas various instances during clinches.
The underdog closed well, but several stanzas were difficult to score. However, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
Buatsi advances, but with the caliber of hard hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Hatton Memorial Fuels All-Manchester Contest
In the co-main event, Arthur defeated Rea by close verdict in a excellent local rivalry battle to secure the European light heavyweight title.
The venue fell silent for a extremely emotional homage ahead of the contest as 10 bells tolled in memory of local hero Ricky Hatton, who passed away 46 years old in last month.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the final chime faded, the quiet gave way to a chant of "only one Hatton".
The fighting within the ring matched the sentiment. Arthur was sent to the canvas by a left hook squarely on the chin in the early round, getting up unsteadily to his position on the referee's count.
But the red-colored shorts of Arthur soon came forward again. From the other corner, the opponent - in opposing blue - was injured early, heavy swelling appearing under his orbital area as the pair traded powerful shots.
Rea, twenty-seven, connected with strong blows but Arthur, 34, matched the intensity with powerful upward punches as the pace seldom decreased over twelve rounds.
The victor edged the verdict with official scores of even score, 115-113 and clearer margin, but both fighters were persistent and brave, everything their idol Hatton stood for.
