British light-heavyweight Joshua Buatsi made a winning yet disappointing debut to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a majority decision in a competitive ten-round contest at the Co-op Live Arena.
But the challenger found success, delivering effective individual punches in a match where the techniques didn't complement each other, with excessive holding disrupting the fight.
Two judges judged it 96-94 to Buatsi, with the remaining official a even score.
"It wasn't my finest performance but what do champions do? They win," Buatsi commented in the ring as he was greeted with disapproval from the spectators.
The Londoner got back to winning after his maiden career setback - an thrilling contest with his previous opponent in February - to secure a 20th pro success.
Several boxing experts believed the challenger, thirty-one, merited the victory but the contender experienced the second defeat of his 28-match career.
The Champion Earns Triumph in Uneventful Affair
The fighter's advancement has stalled in recent times through promotional disputes and extended periods of inactivity.
Earlier forecast as the next star of British boxing, he now stands trying to achieve expectations - possibly in what seems like a ultimate opportunity - under fresh management.
He began cautiously, with the two boxers willing to overcommit in a tentative initial rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second appearance at the higher weight class.
By the fight's midpoint, the underdog had kept it close, causing problems for Buatsi, who operated with a protective stance to narrowly win the cleaner periods.
The spectators' acceptance decreased because of frequent holding, with the challenger going down several times during close exchanges.
The underdog ended stronger, but several stanzas were challenging to assess. However, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, giving Buatsi just one round.
The victor advances, but with the presence of hard hitter David Benavidez, and Russian star Dmitry Bivol ruling the division, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Homage Fuels Manchester Derby Battle
In the co-main event, Lyndon Arthur overcame Bradley Rea by divided decision in a excellent Manchester vs Manchester battle to capture the European light-heavyweight belt.
The arena became quiet for a profoundly moving tribute before the fight as ten bells rang in remembrance of the city's native Ricky Hatton, who died aged 46 in recently.
It was the initial significant broadcast match card in the urban center since Hatton's passing. As the last bell ended, the quiet gave way to a roar of "there's just one Hatton".
The fighting inside the ropes reflected the sentiment. Arthur was sent to the canvas by a left hook directly to the face in the early round, standing uncertainly to his feet on the referee's count.
But the traditional red equipment of the fighter soon came forward again. On the opposite side, the opponent - in competitive blue - was injured soon, heavy swelling developing under his orbital area as the duo exchanged powerful shots.
Rea, 27, delivered effective strikes but Arthur, thirty-four, responded in kind with powerful upward punches as the action rarely dropped over 12 rounds.
Arthur edged the decision with judges scorecards of draw, close margin and wider gap, but the two athletes were relentless and courageous, all the qualities their inspiration Hatton represented.
