British light-heavyweight Buatsi made a winning yet underwhelming debut to life under recent management with a unanimous decision over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a majority decision in a competitive ten-round fight at the boxing arena.
But Parker found success, landing some telling individual punches in a match where the styles failed to mesh, with frequent clinching marring the contest.
The officials had it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my best showing but what defines champions? They prevail," Buatsi stated in the ringside as he was met by boos from the audience.
The British fighter bounced back after his initial pro loss - an thrilling contest with his previous opponent in last winter - to claim a 20th pro success.
Some ringside observers felt the challenger, 31, should have been awarded the win but the contender experienced the second defeat of his 28-fight professional journey.
The Champion Secures Victory in Slow Encounter
His career development has slowed in recent times through promotional disputes and extended periods of lack of fights.
Previously predicted as the rising talent of British boxing, he now finds himself trying to realize his potential - perhaps in what appears to be a final roll of the dice - under recent support.
He started carefully, with the two boxers willing to take risks in a tentative opening few rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second fight at the higher weight class.
By the fight's midpoint, Parker had kept it close, making life awkward for the favorite, who utilized a protective stance to narrowly win the more effective rounds.
The crowd's patience wore thin because of regular grabbing, with Parker slipping to the canvas several times during close exchanges.
Parker finished the stronger, but many rounds were hard to judge. Nevertheless, ex-champion the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, awarding Buatsi just a single round.
Buatsi advances, but with the caliber of heavy hitter Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - judging by this showing - still appears challenging.
Hatton Tribute Fuels Local Rivalry Battle
In the supporting bout, Arthur defeated Bradley Rea by divided decision in a terrific Manchester vs Manchester fight to win the European light heavyweight belt.
The stadium fell silent for a extremely emotional tribute prior to the bout as a bell ceremony rang in memory of local hero Ricky Hatton, who died at age 46 in last month.
It was the initial significant broadcast fight night in the urban center since Hatton's death. As the last bell faded, the silence became a shout of "only one Hatton".
The competition within the ring reflected the emotion. Arthur was sent to the canvas by a powerful punch flush on the chin in the second round, getting up unsteadily to his position on the referee's count.
But the Manchester United-red attire of Arthur soon advanced again. On the opposite side, the opponent - in competitive blue - was marked up soon, significant bruising appearing under his orbital area as the fighters traded powerful shots.
Rea, 27, landed power punches but Arthur, thirty-four, matched the intensity with effective uppercuts as the pace seldom decreased over the full distance.
The victor barely secured the result with judges scorecards of 114-114, narrow lead and wider gap, but the two athletes were persistent and brave, exactly what their inspiration the legend embodied.
