British light heavyweight Joshua Buatsi made a winning yet underwhelming start to life under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a split decision in a competitive ten-round fight at the boxing arena.
But Parker found success, landing some telling single shots in a match where the styles didn't complement each other, with constant grabbing spoiling the action.
The scoring judges had it 96-94 for to Buatsi, with the final judge a 95-95 draw.
"It wasn't my greatest showing but what defines champions? They win," Buatsi commented in the ring as he was greeted with negative reactions from the audience.
The Londoner got back to winning after his initial pro loss - an thrilling contest with his previous opponent in last winter - to earn a twentieth professional win.
Various analysts felt the challenger, 31, merited the decision but the British boxer experienced the second defeat of his 28-match professional journey.
Buatsi Earns Triumph in Uneventful Encounter
Buatsi's progress has slowed in recent years through contract problems and considerable time of inactivity.
Once tipped as the future of UK boxing, he now is positioned trying to achieve expectations - perhaps in what feels like a ultimate opportunity - under recent support.
He opened tentatively, with the two boxers prepared to overcommit in a calculated initial rounds.
Parker, whose single earlier setback came at the lower weight class against his former opponent in two years ago after breaking his hand mid-fight, was making just his second fight at light heavyweight.
By the middle rounds, Parker had made it competitive, creating difficulties for Buatsi, who worked behind a solid defense to narrowly win the cleaner rounds.
The crowd's patience decreased during regular grabbing, with the challenger slipping to the canvas several times during close exchanges.
Parker finished the stronger, but several stanzas were difficult to score. Although, former world champion Carl Frampton - commentating on the broadcast network - had it strongly leaning for the challenger, giving Buatsi just one round.
The victor progresses, but with the presence of hard hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Tribute Fuels All-Manchester Contest
In the co-main event, Arthur defeated Rea by close verdict in a outstanding Manchester vs Manchester contest to secure the continental title.
The venue fell silent for a extremely emotional tribute before the fight as ten bells sounded in remembrance of the city's native Hatton, who passed away aged 46 in recently.
It was the initial significant broadcast boxing event in the urban center since the passing of Hatton. As the concluding sound disappeared, the silence became a shout of "there's just one Hatton".
The fighting during the bout equaled the emotion. The eventual winner was knocked down by a left hook squarely on the jaw in the second round, standing uncertainly to his footing on the referee's count.
But the Manchester United-red shorts of the fighter soon advanced again. Across the ring, the opponent - in opposing blue - was injured early, heavy swelling forming under his orbital area as the pair landed punishing blows.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with powerful upward punches as the action rarely dropped over twelve rounds.
Arthur barely secured the result with official scores of draw, close margin and 115-112, but each competitor were relentless and courageous, all the qualities their inspiration the legend stood for.
