UK light heavyweight Buatsi earned a win yet underwhelming start to his career under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a majority decision in a tight 10-round fight at the Co-op Live Arena.
But the challenger found success, landing some telling clean blows in a contest where the techniques never quite clicked, with excessive holding marring the contest.
The scoring judges had it 96-94 for to the winner, with the remaining official a even score.
"It wasn't my greatest performance but what defines champions? They succeed," the victor commented in the ring as he was faced boos from the spectators.
The Londoner returned to winning ways after his maiden career setback - an epic battle with Callum Smith in last winter - to earn a twentieth professional win.
Some ringside observers believed the challenger, 31, deserved the win but the Derbyshire fighter suffered the second defeat of his 28-match career.
Buatsi Secures Win in Uneventful Match
His career development has slowed in the past few years through management issues and long spells of inactivity.
Once tipped as the future of the British fight scene, he now stands trying to realize his potential - possibly in what appears to be a final roll of the dice - under fresh management.
He began cautiously, with the two boxers prepared to overcommit in a cagey early stages.
Parker, 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 bout at light heavyweight.
By the halfway stage, Parker had stayed in contention, causing problems for Buatsi, who utilized a protective stance to edge the better periods.
The audience's tolerance decreased during frequent holding, with the challenger going down various instances during close exchanges.
The underdog finished the stronger, but multiple periods were difficult to score. However, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it particularly wide for the challenger, awarding Buatsi just a single round.
The victor moves on, but with the caliber of heavy hitter David Benavidez, and Russian champion Bivol ruling the division, the road to world glory - based on this performance - still seems difficult.
Ricky Hatton Homage Motivates Manchester Derby Contest
In the supporting bout, Arthur beat Bradley Rea by close verdict in a outstanding all-Manchester battle to secure the European light heavyweight belt.
The arena grew hushed for a deeply poignant memorial prior to the bout as 10 bells tolled in remembrance of local hero Hatton, who passed away at age 46 in recently.
It was the initial significant broadcast boxing event in the city since Hatton's death. As the final chime disappeared, the stillness gave way to a shout of "there's just one Ricky Hatton".
The action within the ring equaled the sentiment. Arthur was floored by a powerful punch flush on the face in the early round, getting up unsteadily to his feet on the count of eight.
But the traditional red attire of Arthur soon came forward again. On the opposite side, the opponent - in opposing blue - was damaged quickly, heavy swelling developing under his face as the duo exchanged hard punches.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, responded in kind with effective uppercuts as the pace hardly diminished over the full distance.
The victor narrowly won the result with official scores of draw, 115-113 and 115-112, but both fighters were relentless and courageous, exactly what their idol the legend represented.
