British light heavyweight Buatsi secured a victory yet underwhelming start to his career under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a close ten-round bout at the Co-op Live Arena.
But Parker had his moments, connecting with powerful individual punches in a match where the styles didn't complement each other, with constant grabbing marring the contest.
Two judges had it 96-94 to the winner, with the third a even score.
"It wasn't my best performance but how do champions respond? They succeed," Buatsi commented in the ringside as he was met by negative reactions from the crowd.
The Londoner bounced back after his maiden career setback - an thrilling contest with his previous opponent in last winter - to claim a 20th pro success.
Some ringside observers felt the challenger, 31, merited the victory but the contender experienced the second defeat of his 28-match career.
The Champion Claims Win in Dull Match
His career development has plateaued in recent times through contract problems and long spells of inactivity.
Previously predicted as the future of the British fight scene, he now stands trying to realize his potential - maybe in what seems like a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter willing to take risks in a tentative opening few rounds.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second appearance at light heavyweight.
By the middle rounds, the underdog had made it competitive, making life awkward for Buatsi, who operated with a solid defense to barely take the better stanzas.
The audience's tolerance wore thin because of frequent holding, with the challenger slipping to the canvas multiple occasions during close exchanges.
Parker closed well, but several stanzas were challenging to assess. Nevertheless, former world champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
Buatsi advances, but with the likes of heavy hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still looks steep.
Hatton Tribute Inspires Local Rivalry Battle
In the co-main event, Arthur overcame Rea by divided decision in a excellent local rivalry battle to capture the European light heavyweight belt.
The arena fell silent for a extremely emotional tribute before the fight as a bell ceremony rang in memory of Manchester's own Hatton, who died at age 46 in recently.
It was the first major televised boxing event in the location since Hatton's passing. As the last bell ended, the quiet became a chant of "there's only one Ricky Hatton".
The fighting within the ring matched the feeling. Arthur was sent to the canvas by a powerful punch squarely on the face in the early round, rising shakily to his footing on the count of eight.
But the traditional red equipment of Arthur soon advanced again. From the other corner, Rea - in opposing blue - was marked up quickly, noticeable damage developing under his face as the pair traded hard punches.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, fought fire with fire with powerful upward punches as the intensity rarely dropped over the full distance.
The victor edged the result with official scores of 114-114, close margin and clearer margin, but the two athletes were relentless and courageous, everything their idol Hatton stood for.
