British light-heavyweight Buatsi secured a victory yet disappointing start to life under new promoters with a points victory over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a close 10-round contest at the boxing arena.
But the challenger landed significant shots, connecting with powerful single shots in a fight where the approaches failed to mesh, with constant grabbing marring the fight.
The scoring judges judged it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my best performance but how do champions respond? They succeed," Buatsi commented in the ringside as he was faced negative reactions from the crowd.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in February - to earn a 20th pro success.
Various analysts thought the challenger, 31, should have been awarded the victory but the British boxer suffered the second defeat of his 28-match career.
Buatsi Secures Triumph in Dull Affair
Buatsi's progress has slowed in recent years through management issues and long spells of inactivity.
Previously predicted as the future of British boxing, he now finds himself trying to achieve expectations - possibly in what feels like a final roll of the dice - under recent support.
He started carefully, with both competitors prepared to take risks in a cagey initial rounds.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after damaging his hand during the bout, was participating in his second appearance at light heavyweight.
By the halfway stage, Parker had stayed in contention, causing problems for Buatsi, who operated with a solid defense to edge the better periods.
The audience's tolerance wore thin because of frequent holding, with the challenger falling to the floor multiple occasions during close exchanges.
Parker finished the stronger, but several stanzas were difficult to score. However, ex-champion the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, awarding Buatsi just a single round.
Buatsi progresses, but with the caliber of hard hitter David Benavidez, and Russian star Bivol leading the category, the road to world glory - judging by this showing - still seems difficult.
Hatton Tribute Inspires Manchester Derby Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by split-decision in a excellent Manchester vs Manchester fight to secure the European light heavyweight championship.
The stadium fell silent for a extremely emotional memorial prior to the bout as ten bells sounded in remembrance of Manchester's own Hatton, who succumbed aged 46 in recently.
It was the first major televised match card in the urban center since the passing of Hatton. As the concluding sound faded, the quiet transitioned to a chant of "there's just one Ricky Hatton".
The competition during the bout reflected the emotion. The eventual winner was knocked down by a significant blow directly to the chin in the initial stage, getting up unsteadily to his feet on the count of eight.
But the Manchester United-red attire of Arthur soon advanced again. From the other corner, the opponent - in opposing blue - was injured early, noticeable damage developing under his face as the duo exchanged powerful shots.
The challenger, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the action rarely dropped over 12 rounds.
Arthur barely secured the verdict with judges scorecards of draw, close margin and clearer margin, but each competitor were determined and courageous, all the qualities their idol Hatton represented.
