UK light heavyweight Joshua Buatsi secured a victory yet unimpressive debut to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a competitive 10-round contest at the boxing arena.
But Parker found success, delivering effective clean blows in a contest where the techniques never quite clicked, with constant grabbing spoiling the action.
The officials scored it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my best performance but how do champions respond? They win," Buatsi said in the arena as he was greeted with boos from the audience.
The Londoner bounced back after his initial pro loss - an memorable fight with his previous opponent in February - to earn a 20th career victory.
Some ringside observers felt the challenger, thirty-one, merited the win but the contender suffered the second loss of his 28-fight professional journey.
The Champion Claims Victory in Uneventful Encounter
His career development has slowed in the past few years through promotional disputes and extended periods of inactivity.
Earlier forecast as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - perhaps in what feels like a last chance - under recent support.
He started carefully, with the two boxers prepared to overcommit in a cagey initial rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after suffering a hand injury in the contest, was making just his second appearance at light heavyweight.
By the fight's midpoint, the underdog had kept it close, making life awkward for Buatsi, who operated with a protective stance to narrowly win the cleaner periods.
The crowd's patience wore thin amid constant clinching, with Parker falling to the floor several times during grappling.
The underdog ended stronger, but several stanzas were hard to judge. Although, ex-champion Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, giving Buatsi just only one stanza.
Buatsi advances, but with the caliber of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Hatton Homage Inspires All-Manchester Contest
In the co-main event, Arthur overcame Rea by split-decision in a excellent all-Manchester contest to capture the European light-heavyweight title.
The venue grew hushed for a profoundly moving memorial prior to the bout as 10 bells tolled in honor of local hero Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast boxing event in the location since Hatton's passing. As the final chime faded, the silence gave way to a roar of "there's only one Ricky Hatton".
The fighting inside the ropes equaled the feeling. The eventual winner was knocked down by a significant blow flush on the jaw in the second round, rising shakily to his feet on the eight count.
But the red-colored attire of the fighter soon came forward again. Across the ring, the opponent - in competitive blue - was injured early, significant bruising forming under his eye as the fighters exchanged punishing blows.
Rea, 27, delivered effective strikes but Arthur, 34, fought fire with fire with stinging uppercuts as the action rarely dropped over the full distance.
The victor narrowly won the decision with judges scorecards of even score, narrow lead and clearer margin, but the two athletes were determined and brave, all the qualities their hero the legend embodied.
