UK light-heavyweight Buatsi made a winning yet disappointing beginning to life under recent management with a points victory over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a split decision in a close 10-round contest at the boxing arena.
But Parker landed significant shots, delivering effective clean blows in a match where the styles never quite clicked, with frequent clinching spoiling the fight.
The scoring judges judged it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest performance but how do champions respond? They succeed," Buatsi commented in the ring as he was faced boos from the audience.
The Londoner got back to winning after his maiden career setback - an thrilling contest with his previous opponent in February - to earn a 20th career victory.
Various analysts believed the challenger, thirty-one, should have been awarded the decision but the British boxer suffered the second setback of his 28-bout professional journey.
The Champion Secures Win in Uneventful Encounter
His career development has slowed in recent years through management issues and long spells of lack of fights.
Earlier forecast as the future of the British fight scene, he now is positioned trying to achieve expectations - perhaps in what feels like a last chance - under recent support.
He started carefully, with the two boxers ready to take risks in a calculated initial rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second bout at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, making life awkward for the favorite, who operated with a tight guard to edge the more effective stanzas.
The crowd's patience wore thin during frequent holding, with the challenger slipping to the canvas multiple occasions during clinches.
The underdog closed well, but many rounds were difficult to score. Although, previous titleholder the boxing analyst - working with the broadcast network - had it strongly leaning for Parker, awarding Buatsi just a single round.
Buatsi advances, but with the caliber of power puncher David Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - judging by this showing - still appears challenging.
Ricky Hatton Homage Motivates All-Manchester Battle
In the co-main event, Arthur defeated Rea by split-decision in a outstanding Manchester vs Manchester contest to win the European light-heavyweight title.
The venue became quiet for a extremely emotional homage before the fight as a bell ceremony tolled in honor of Manchester's own Hatton, who died at age 46 in September.
It was the first major televised fight night in the urban center since the passing of Hatton. As the concluding sound ended, the silence gave way to a shout of "there's just one Ricky Hatton".
The fighting within the ring reflected the emotion. Arthur was sent to the canvas by a powerful punch flush on the face in the initial stage, standing uncertainly to his feet on the referee's count.
But the Manchester United-red shorts of the fighter soon advanced again. On the opposite side, Rea - in rival City blue - was injured early, noticeable damage appearing under his orbital area as the fighters exchanged powerful shots.
Rea, 27, delivered effective strikes but the champion, thirty-four, matched the intensity with powerful upward punches as the intensity rarely dropped over twelve rounds.
Arthur narrowly won the result with judges scorecards of draw, narrow lead and 115-112, but both fighters were persistent and full of heart, exactly what their hero Hatton embodied.
