UK light heavyweight Buatsi made a winning yet disappointing debut to life under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a tight ten-round fight at the Manchester venue.
But the challenger found success, connecting with powerful single shots in a contest where the styles didn't complement each other, with excessive holding spoiling the fight.
Two judges judged it 96-94 to Buatsi, with the third a 95-95 draw.
"It wasn't my best display but how do champions respond? They succeed," Buatsi stated in the ringside as he was greeted with boos from the crowd.
The British fighter bounced back after his initial pro loss - an thrilling contest with Callum Smith in last winter - to earn a 20th career victory.
Some ringside observers believed Parker, thirty-one, merited the decision but the British boxer endured the second loss of his 28-fight professional journey.
Buatsi Secures Victory in Slow Affair
Buatsi's progress has stalled in recent years through management issues and extended periods of inactivity.
Once tipped as the next star of UK boxing, he now finds himself trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under new promotional backing.
He opened tentatively, with neither fighter prepared to overcommit in a calculated opening few rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in two years ago after breaking his hand during the bout, was participating in his second appearance at light-heavyweight.
By the middle rounds, the underdog had kept it close, creating difficulties for Buatsi, who utilized a protective stance to barely take the better periods.
The audience's tolerance wore thin during constant clinching, with the challenger slipping to the canvas multiple occasions during close exchanges.
Parker closed well, but multiple periods were challenging to assess. However, ex-champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the likes of heavy hitter David Benavidez, and Russian star Bivol leading the category, the journey to titles - on this evidence - still appears challenging.
Ricky Hatton Tribute Fuels Local Rivalry Battle
In the supporting bout, Arthur defeated Bradley Rea by split-decision in a outstanding all-Manchester battle to win the European light-heavyweight title.
The stadium fell silent for a profoundly moving tribute ahead of the contest as ten bells sounded in remembrance of Manchester's own Hatton, who passed away at age 46 in recently.
It was the first major televised boxing event in the location since Hatton's passing. As the final chime disappeared, the silence became a shout of "there's only one Hatton".
The fighting within the ring matched the feeling. Arthur was sent to the canvas by a significant blow squarely on the face in the initial stage, getting up unsteadily to his feet on the eight count.
But the traditional red attire of Arthur soon came forward again. On the opposite side, Rea - in opposing blue - was marked up quickly, noticeable damage forming under his eye as the fighters traded hard punches.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the action hardly diminished over the full distance.
Arthur edged the verdict with official scores of even score, close margin and 115-112, but both fighters were relentless and full of heart, all the qualities their idol the legend stood for.
