UK light heavyweight Buatsi made a winning yet underwhelming debut to life under new promoters with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a split decision in a competitive ten-round bout at the boxing arena.
But Parker landed significant shots, delivering effective clean blows in a fight where the techniques failed to mesh, with constant grabbing disrupting the fight.
Two judges judged it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my greatest showing but how do champions respond? They succeed," the victor commented in the arena as he was met by boos from the audience.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in last winter - to earn a 20th career victory.
Some ringside observers believed the challenger, thirty-one, should have been awarded the decision but the Derbyshire fighter endured the second setback of his 28-bout career.
Buatsi Earns Triumph in Slow Encounter
Buatsi's progress has plateaued in recent years through management issues and considerable time of inactivity.
Previously predicted as the future of the British fight scene, he now is positioned trying to achieve expectations - perhaps in what feels like a ultimate opportunity - under new promotional backing.
He started carefully, with both competitors willing to take risks in a cagey initial rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was making just his second bout at the higher weight class.
By the halfway stage, Parker had made it competitive, creating difficulties for Buatsi, who operated with a solid defense to barely take the cleaner periods.
The crowd's patience wore thin during frequent holding, with Parker falling to the floor multiple occasions during clinches.
The underdog finished the stronger, but multiple periods were hard to judge. Nevertheless, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just a single round.
Buatsi moves on, but with the caliber of power puncher David Benavidez, and Russian star Dmitry Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Hatton Homage Fuels All-Manchester Contest
In the co-main event, Arthur beat Rea by divided decision in a excellent all-Manchester contest to secure the European light heavyweight championship.
The venue grew hushed for a extremely emotional memorial before the fight as 10 bells sounded in remembrance of Manchester's own Ricky Hatton, who died 46 years old in last month.
It was the initial significant broadcast match card in the location since the passing of Hatton. As the final chime ended, the silence transitioned to a roar of "there's just one Ricky Hatton".
The competition during the bout equaled the sentiment. The eventual winner was sent to the canvas by a significant blow squarely on the chin in the initial stage, rising shakily to his footing on the count of eight.
But the Manchester United-red attire of Arthur soon pressed ahead again. From the other corner, the opponent - in rival City blue - was marked up early, heavy swelling developing under his eye as the fighters exchanged punishing blows.
The challenger, twenty-seven, landed power punches but the champion, thirty-four, fought fire with fire with powerful upward punches as the intensity hardly diminished over twelve rounds.
The victor edged the decision with official scores of 114-114, 115-113 and 115-112, but each competitor were determined and brave, exactly what their idol Hatton stood for.
