UK light-heavyweight Joshua Buatsi made a winning yet underwhelming start to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a close ten-round contest at the Manchester venue.
But Parker found success, delivering effective single shots in a contest where the techniques didn't complement each other, with excessive holding marring the action.
The officials judged it 96-94 to the winner, with the third a even score.
"It wasn't my finest showing but what do champions do? They succeed," Buatsi stated in the ringside as he was faced boos from the crowd.
The Londoner got back to winning after his maiden career setback - an epic battle with his previous opponent in February - to claim a 20th career victory.
Several boxing experts thought Parker, 31, deserved the win but the contender experienced the second setback of his 28-bout professional journey.
The Champion Secures Triumph in Uneventful Encounter
Buatsi's progress has plateaued in recent times through management issues and considerable time of inactivity.
Earlier forecast as the future of the British fight scene, he now is positioned trying to fulfil that early promise - possibly in what seems like a last chance - under fresh management.
He began cautiously, with neither fighter prepared to take risks in a tentative initial rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after damaging his hand during the bout, was competing in only his second appearance at light heavyweight.
By the fight's midpoint, Parker had made it competitive, making life awkward for the favorite, who operated with a solid defense to barely take the more effective rounds.
The spectators' acceptance wore thin amid regular grabbing, with the challenger falling to the floor several times during close exchanges.
Parker finished the stronger, but many rounds were hard to judge. Although, former world champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, giving Buatsi just only one stanza.
The victor advances, but with the presence of hard hitter David Benavidez, and Russian star Bivol ruling the division, the road to world glory - judging by this showing - still looks steep.
Ricky Hatton Tribute Fuels Local Rivalry Fight
In the co-main event, Arthur overcame Rea by divided decision in a terrific local rivalry battle to win the European light heavyweight belt.
The arena grew hushed for a deeply poignant memorial prior to the bout as a bell ceremony sounded in remembrance of local hero Ricky Hatton, who died 46 years old in recently.
It was the first major televised fight night in the urban center since the passing of Hatton. As the concluding sound ended, the stillness transitioned to a roar of "only one Hatton".
The competition within the ring reflected the sentiment. The eventual winner was sent to the canvas by a powerful punch flush on the face in the initial stage, getting up unsteadily to his position on the count of eight.
But the red-colored shorts of the fighter soon advanced again. On the opposite side, the opponent - in competitive blue - was marked up soon, heavy swelling forming under his face as the duo traded hard punches.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, matched the intensity with powerful upward punches as the pace hardly diminished over the full distance.
The victor narrowly won the result with judges scorecards of draw, 115-113 and wider gap, but both fighters were persistent and brave, everything their idol the legend embodied.
