UK light-heavyweight Buatsi earned a win yet underwhelming debut to his career under recent management with a unanimous decision over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a majority decision in a tight 10-round fight at the boxing arena.
But Parker found success, landing some telling clean blows in a match where the approaches didn't complement each other, with frequent clinching spoiling the action.
Two judges had it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my finest performance but how do champions respond? They succeed," Buatsi commented in the ring as he was met by negative reactions from the audience.
The Londoner returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in last winter - to claim a twentieth professional win.
Various analysts believed the challenger, 31, should have been awarded the win but the Derbyshire fighter experienced the second defeat of his 28-bout professional journey.
The Champion Secures Triumph in Slow Match
His career development has stalled in recent years through management issues and extended periods of inactivity.
Previously predicted as the rising talent of UK boxing, he now is positioned trying to realize his potential - possibly in what appears to be a final roll of the dice - under recent support.
He started carefully, with neither fighter willing to take risks in a cagey early stages.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after breaking his hand in the contest, was competing in only his second appearance at light heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for the favorite, who utilized a protective stance to barely take the better periods.
The audience's tolerance wore thin amid regular grabbing, with the challenger going down multiple occasions during grappling.
Parker closed well, but several stanzas were difficult to score. Although, former world champion Carl Frampton - providing analysis for the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
Buatsi advances, but with the presence of power puncher David Benavidez, and Eastern European fighter Bivol leading the category, the road to world glory - based on this performance - still appears challenging.
Hatton Memorial Motivates Manchester Derby Fight
In the co-main event, Arthur overcame Bradley Rea by split-decision in a outstanding Manchester vs Manchester battle to win the European light-heavyweight belt.
The stadium grew hushed for a profoundly moving homage ahead of the contest as a bell ceremony tolled in remembrance of local hero Ricky Hatton, who succumbed aged 46 in September.
It was the premier televised boxing event in the urban center since Hatton's passing. As the last bell ended, the stillness gave way to a chant of "there's just one Ricky Hatton".
The action inside the ropes equaled the feeling. Arthur was sent to the canvas by a left hook flush on the jaw in the early round, standing uncertainly to his feet on the referee's count.
But the Manchester United-red shorts of Arthur soon came forward again. Across the ring, the opponent - in competitive blue - was damaged quickly, heavy swelling developing under his face as the pair exchanged punishing blows.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, responded in kind with effective uppercuts as the action rarely dropped over 12 rounds.
Arthur edged the verdict with official scores of even score, narrow lead and clearer margin, but both fighters were determined and full of heart, exactly what their idol Hatton embodied.
