UK light heavyweight Buatsi secured a victory yet underwhelming start to life under recent management with a unanimous decision over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a split decision in a competitive ten-round bout at the Manchester venue.
But Parker landed significant shots, delivering effective individual punches in a contest where the styles didn't complement each other, with constant grabbing spoiling the action.
Two judges scored it 96-94 for to the winner, with the third a even score.
"It wasn't my finest performance but how do champions respond? They prevail," Buatsi stated in the ring as he was met by negative reactions from the crowd.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in February - to earn a 20th pro success.
Some ringside observers believed Parker, thirty-one, deserved the decision but the contender experienced the second defeat of his 28-fight professional journey.
Buatsi Secures Triumph in Uneventful Encounter
His career development has slowed in recent times through promotional disputes and extended periods of inactivity.
Earlier forecast as the next star of UK boxing, he now stands trying to realize his potential - possibly in what seems like a final roll of the dice - under new promotional backing.
He began cautiously, with both competitors prepared to take risks in a tentative early stages.
Parker, whose only previous defeat came at super middleweight against John Ryder in two years ago after breaking his hand during the bout, was competing in only his second appearance at light heavyweight.
By the fight's midpoint, the underdog had stayed in contention, creating difficulties for Buatsi, who operated with a solid defense to edge the more effective periods.
The crowd's patience decreased because of regular grabbing, with Parker slipping to the canvas multiple occasions during clinches.
The underdog ended stronger, but many rounds were challenging to assess. However, former world champion the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the likes of hard hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Hatton Homage Motivates Local Rivalry Battle
In the co-main event, Lyndon Arthur beat Rea by split-decision in a excellent all-Manchester contest to secure the continental championship.
The arena fell silent for a extremely emotional tribute ahead of the contest as ten bells sounded in honor of the city's native Hatton, who died aged 46 in September.
It was the premier televised fight night in the city since Hatton's death. As the concluding sound ended, the quiet gave way to a roar of "there's just one Ricky Hatton".
The action inside the ropes matched the feeling. Arthur was sent to the canvas by a left hook directly to the jaw in the early round, standing uncertainly to his feet on the referee's count.
But the traditional red attire of Arthur soon advanced again. From the other corner, the opponent - in rival City blue - was marked up quickly, noticeable damage appearing under his face as the fighters exchanged powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, 34, matched the intensity with effective uppercuts as the pace rarely dropped over the full distance.
Arthur barely secured the verdict with judges scorecards of even score, narrow lead and wider gap, but each competitor were determined and brave, all the qualities their hero the legend embodied.
