British light-heavyweight Buatsi made a winning yet unimpressive debut to life under fresh promotional backing with a points victory over Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a majority decision in a tight ten-round contest at the Manchester venue.
But the challenger landed significant shots, delivering effective clean blows in a match where the styles failed to mesh, with frequent clinching spoiling the fight.
The officials had it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my best showing but how do champions respond? They prevail," Buatsi stated in the ringside as he was greeted with disapproval from the audience.
The British fighter returned to winning ways after his initial pro loss - an thrilling contest with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers felt Parker, thirty-one, should have been awarded the victory but the Derbyshire fighter suffered the second defeat of his 28-bout professional journey.
Buatsi Secures Victory in Uneventful Encounter
His career development has stalled in recent times through contract problems and extended periods of inactivity.
Earlier forecast as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - possibly in what appears to be a ultimate opportunity - under new promotional backing.
He began cautiously, with neither fighter ready to take risks in a tentative early stages.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was making just his second bout at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, causing problems for Buatsi, who utilized a protective stance to edge the better rounds.
The spectators' acceptance diminished because of regular grabbing, with Parker falling to the floor multiple occasions during grappling.
The underdog closed well, but many rounds were challenging to assess. Although, former world champion the boxing analyst - commentating on Dazn - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi moves on, but with the likes of hard hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still appears challenging.
Hatton Homage Motivates Manchester Derby Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by close verdict in a outstanding all-Manchester contest to secure the European light heavyweight belt.
The stadium grew hushed for a extremely emotional homage prior to the bout as ten bells tolled in honor of local hero Ricky Hatton, who died at age 46 in recently.
It was the first major televised boxing event 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 competition within the ring matched the feeling. Arthur was knocked down by a left hook squarely on the face in the initial stage, rising shakily to his position on the eight count.
But the traditional red equipment of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was marked up early, heavy swelling appearing under his orbital area as the duo landed powerful shots.
The challenger, twenty-seven, landed power punches but the champion, 34, responded in kind with powerful upward punches as the pace rarely dropped over the full distance.
Arthur edged the verdict with scoring tallies of 114-114, close margin and clearer margin, but both fighters were relentless and full of heart, everything their idol the legend stood for.
