UK light-heavyweight Joshua Buatsi made a winning yet underwhelming debut to life under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a close 10-round contest at the boxing arena.
But Parker had his moments, landing some telling single shots in a match where the techniques never quite clicked, with frequent clinching spoiling the fight.
The scoring judges judged it 96-94 for to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest performance but how do champions respond? They win," the victor stated in the ringside as he was faced disapproval from the spectators.
The British fighter bounced back after his first professional defeat - an thrilling contest with his previous opponent in last winter - to claim a twentieth professional win.
Some ringside observers believed the challenger, 31, deserved the victory but the British boxer experienced the second setback of his 28-match career.
The Champion Claims Victory in Uneventful Encounter
The fighter's advancement has stalled in recent years through promotional disputes and long spells of inactivity.
Earlier forecast as the next star of UK boxing, he now stands trying to fulfil that early promise - possibly in what feels like a last chance - under recent support.
He opened tentatively, with the two boxers willing to take risks in a calculated early stages.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was making just his second bout at light-heavyweight.
By the middle rounds, the underdog had kept it close, making life awkward for the favorite, who operated with a tight guard to narrowly win the more effective periods.
The spectators' acceptance wore thin amid constant clinching, with the challenger falling to the floor various instances during clinches.
The underdog ended stronger, but many rounds were challenging to assess. However, former world champion Carl Frampton - commentating on the broadcast network - had it significantly in favor for Parker, awarding Buatsi just one round.
The victor advances, but with the likes of power puncher David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still looks steep.
Hatton Homage Motivates Local Rivalry Battle
In the co-main event, Lyndon Arthur overcame Bradley Rea by divided decision in a excellent Manchester vs Manchester fight to win the continental title.
The arena became quiet for a profoundly moving tribute before the fight as a bell ceremony tolled in remembrance of Manchester's own Hatton, who succumbed at age 46 in September.
It was the premier televised fight night in the location since Hatton's passing. As the concluding sound disappeared, the quiet became a shout of "there's just one Ricky Hatton".
The action inside the ropes equaled the feeling. Arthur was floored by a left hook flush on the jaw in the second round, rising shakily to his footing on the eight count.
But the traditional red equipment of the fighter soon came forward again. From the other corner, the opponent - in competitive blue - was marked up soon, noticeable damage appearing under his eye as the duo traded punishing blows.
Rea, twenty-seven, connected with strong blows but Arthur, 34, responded in kind with effective uppercuts as the intensity rarely dropped over 12 rounds.
Arthur narrowly won the result with scoring tallies of even score, 115-113 and clearer margin, but both fighters were determined and brave, all the qualities their idol the legend stood for.
