British light-heavyweight Joshua Buatsi made a winning yet disappointing debut to his career under new promoters with a unanimous decision over Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a judges' verdict in a close 10-round fight at the Co-op Live Arena.
But Parker landed significant shots, delivering effective individual punches in a match where the techniques didn't complement each other, with frequent clinching marring the action.
The officials scored it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my finest showing but how do champions respond? They prevail," the victor stated in the ringside as he was greeted with disapproval from the audience.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in February - to claim a 20th career victory.
Various analysts thought the challenger, 31, merited the victory but the British boxer experienced the second setback of his 28-bout career.
The Champion Claims Win in Uneventful Match
The fighter's advancement has stalled in recent years through management issues and considerable time of lack of fights.
Once tipped as the rising talent of British boxing, he now stands trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under recent support.
He opened tentatively, with the two boxers prepared to overcommit in a calculated opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after damaging his hand mid-fight, was making just his second bout at light heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who utilized a protective stance to narrowly win the more effective periods.
The crowd's patience diminished because of regular grabbing, with the challenger falling to the floor various instances during close exchanges.
The underdog finished the stronger, but multiple periods were difficult to score. Nevertheless, former world champion the boxing analyst - providing analysis for Dazn - had it significantly in favor for Parker, scoring for Buatsi just a single round.
Buatsi moves on, but with the presence of heavy hitter David Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - based on this performance - still looks steep.
Hatton Tribute Motivates Manchester Derby Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by split-decision in a excellent local rivalry fight to secure the European light-heavyweight belt.
The venue grew hushed for a extremely emotional tribute prior to the bout as 10 bells sounded in memory of the city's native Hatton, who passed away aged 46 in September.
It was the premier televised match card in the city since Hatton's passing. As the last bell disappeared, the quiet became a roar of "there's just one Ricky Hatton".
The action inside the ropes reflected the emotion. Arthur was floored by a significant blow flush on the jaw in the early round, rising shakily to his feet on the referee's count.
But the traditional red equipment of Arthur soon advanced again. From the other corner, Rea - in opposing blue - was damaged soon, heavy swelling developing under his eye as the duo traded hard punches.
Rea, 27, connected with strong blows but the champion, 34, matched the intensity with effective uppercuts as the intensity rarely dropped over twelve rounds.
The victor edged the verdict with official scores of 114-114, narrow lead and wider gap, but each competitor were relentless and brave, everything their inspiration Hatton stood for.
