British light heavyweight Buatsi secured a victory yet unimpressive beginning to life under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a split decision in a tight 10-round fight at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling single shots in a contest where the styles never quite clicked, with constant grabbing spoiling the fight.
The officials had it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my greatest display but what defines champions? They win," Buatsi said in the ringside as he was greeted with disapproval from the spectators.
The British fighter returned to winning ways after his initial pro loss - an epic battle with his previous opponent in February - to secure a 20th career victory.
Various analysts believed Parker, thirty-one, should have been awarded the decision but the British boxer experienced the second loss of his 28-bout career.
The Champion Earns Triumph in Dull Match
The fighter's advancement has stalled in the past few years through management issues and considerable time of inactivity.
Once tipped as the rising talent of UK boxing, he now finds himself trying to achieve expectations - maybe in what seems like a last chance - under recent support.
He began cautiously, with both competitors ready to be aggressive in a tentative initial rounds.
Parker, whose sole prior loss came at super-middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was participating in his second appearance at the higher weight class.
By the halfway stage, Parker had made it competitive, causing problems for Buatsi, who operated with a protective stance to barely take the more effective stanzas.
The audience's tolerance wore thin amid regular grabbing, with the challenger falling to the floor several times during close exchanges.
Parker closed well, but multiple periods were difficult to score. Although, former world champion the boxing analyst - working with Dazn - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
The victor moves on, but with the caliber of hard hitter David Benavidez, and Russian star Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Memorial Fuels Manchester Derby Battle
In the secondary fight, Arthur overcame Bradley Rea by divided decision in a outstanding local rivalry battle to secure the European light heavyweight championship.
The arena became quiet for a deeply poignant tribute before the fight as 10 bells sounded in honor of Manchester's own Ricky Hatton, who passed away 46 years old in September.
It was the first major televised fight night in the urban center since Hatton's death. As the final chime disappeared, the silence gave way to a chant of "there's just one Ricky Hatton".
The fighting inside the ropes matched the sentiment. Arthur was knocked down by a left hook flush on the chin in the early round, standing uncertainly to his footing on the referee's count.
But the red-colored shorts of the fighter soon pressed ahead again. Across the ring, the opponent - in opposing blue - was damaged soon, significant bruising appearing under his face as the duo traded powerful shots.
Rea, 27, landed power punches but the champion, thirty-four, responded in kind with powerful upward punches as the intensity seldom decreased over 12 rounds.
Arthur narrowly won the verdict with official scores of even score, close margin and 115-112, but each competitor were relentless and full of heart, exactly what their idol the legend represented.
