UK light-heavyweight Joshua Buatsi earned a win yet unimpressive beginning to life under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a judges' verdict in a competitive ten-round contest at the boxing arena.
But Parker had his moments, landing some telling individual punches in a fight where the approaches failed to mesh, with constant grabbing disrupting the action.
The scoring judges had it 96-94 for to Buatsi, with the third a even score.
"It wasn't my finest performance but how do champions respond? They prevail," Buatsi stated in the ringside as he was met by boos from the audience.
The British fighter got back to winning after his first professional defeat - an memorable fight with Callum Smith in February - to claim a 20th career victory.
Various analysts felt the challenger, 31, should have been awarded the win but the British boxer endured the second loss of his 28-fight professional journey.
Buatsi Claims Win in Slow Affair
His career development has slowed in recent times through promotional disputes and long spells of lack of fights.
Once tipped as the future of British boxing, he now stands trying to realize his potential - perhaps in what seems like a final roll of the dice - under recent support.
He started carefully, with the two boxers willing to take risks in a cagey opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was participating in his second bout at light-heavyweight.
By the middle rounds, Parker had made it competitive, making life awkward for the favorite, who operated with a solid defense to edge the cleaner periods.
The spectators' acceptance wore thin amid constant clinching, with the challenger slipping to the canvas multiple occasions during grappling.
The underdog closed well, but many rounds were challenging to assess. Nevertheless, former world champion the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, awarding Buatsi just a single round.
Buatsi advances, but with the likes of power puncher Benavidez, and Eastern European fighter Bivol leading the category, the path to championship success - based on this performance - still looks steep.
Hatton Homage Motivates Local Rivalry Fight
In the supporting bout, Lyndon Arthur beat Rea by split-decision in a outstanding local rivalry battle to capture the continental belt.
The stadium became quiet for a deeply poignant tribute ahead of the contest as 10 bells tolled in memory of the city's native Ricky Hatton, who succumbed aged 46 in last month.
It was the premier televised boxing event in the city since Hatton's death. As the last bell ended, the stillness became a shout of "there's just one Ricky Hatton".
The action inside the ropes reflected the emotion. The eventual winner was floored by a left hook flush on the jaw in the initial stage, rising shakily to his footing on the eight count.
But the traditional red attire of Arthur soon pressed ahead again. Across the ring, Rea - in rival City blue - was damaged soon, significant bruising appearing under his orbital area as the pair exchanged punishing blows.
Rea, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with effective uppercuts as the pace rarely dropped over the full distance.
Arthur edged the decision with scoring tallies of draw, 115-113 and wider gap, but each competitor were determined and brave, everything their inspiration the legend stood for.
