British light heavyweight Buatsi made a winning yet unimpressive beginning to his career under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a majority decision in a competitive ten-round bout at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful individual punches in a fight where the techniques never quite clicked, with frequent clinching spoiling the action.
Two judges scored it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my finest performance but what defines champions? They prevail," the victor commented in the arena as he was greeted with negative reactions from the crowd.
The Londoner got back to winning after his initial pro loss - an thrilling contest with his previous opponent in last winter - to claim a 20th pro success.
Some ringside observers believed the challenger, 31, should have been awarded the win but the contender suffered the second defeat of his 28-match professional journey.
The Champion Earns Victory in Dull Affair
The fighter's advancement has stalled in recent years through promotional disputes and extended periods of inactivity.
Earlier forecast as the rising talent of UK boxing, he now stands trying to realize his potential - possibly in what appears to be a ultimate opportunity - under fresh management.
He started carefully, with the two boxers ready to be aggressive in a tentative initial rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in two years ago after damaging his hand in the contest, was participating in his second fight at the higher weight class.
By the middle rounds, the underdog had stayed in contention, creating difficulties for the favorite, who worked behind a tight guard to narrowly win the better rounds.
The spectators' acceptance wore thin because of constant clinching, with Parker going down various instances during close exchanges.
Parker finished the stronger, but several stanzas were challenging to assess. However, ex-champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the caliber of power puncher David Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Homage Motivates Manchester Derby Fight
In the co-main event, Arthur overcame Bradley Rea by close verdict in a excellent all-Manchester battle to capture the European light heavyweight belt.
The arena became quiet for a deeply poignant tribute before the fight as ten bells tolled in honor of local hero Hatton, who died at age 46 in last month.
It was the premier televised fight night in the location since the passing of Hatton. As the final chime disappeared, the quiet became a roar of "there's only one Hatton".
The action inside the ropes equaled the feeling. Arthur was floored by a left hook squarely on the face in the second round, getting up unsteadily to his position on the eight count.
But the red-colored shorts of the fighter soon advanced again. Across the ring, the opponent - in rival City blue - was injured quickly, noticeable damage appearing under his face as the duo traded powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, fought fire with fire with powerful upward punches as the pace seldom decreased over twelve rounds.
The victor narrowly won the decision with official scores of 114-114, close margin and wider gap, but each competitor were determined and full of heart, all the qualities their inspiration Hatton embodied.
