UK light heavyweight Joshua Buatsi made a winning yet disappointing beginning to his career under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a split decision in a close 10-round fight at the Manchester venue.
But Parker found success, delivering effective single shots in a fight where the approaches never quite clicked, with constant grabbing spoiling the action.
Two judges scored it 96-94 in favor to Buatsi, with the remaining official a even score.
"It wasn't my greatest showing but what do champions do? They succeed," the victor commented in the ring as he was greeted with boos from the audience.
The British fighter got back to winning after his maiden career setback - an thrilling contest with his previous opponent in February - to secure a 20th career victory.
Several boxing experts believed the challenger, thirty-one, merited the win but the Derbyshire fighter endured the second defeat of his 28-match professional journey.
The Champion Earns Triumph in Dull Match
The fighter's advancement has slowed in the past few years through management issues and considerable time of lack of fights.
Earlier forecast as the future of UK boxing, he now is positioned trying to realize his potential - maybe in what seems like a last chance - under recent support.
He began cautiously, with neither fighter ready to be aggressive in a tentative early stages.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in two years ago after breaking his hand during the bout, was making just his second appearance at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, creating difficulties for the favorite, who operated with a protective stance to edge the cleaner stanzas.
The audience's tolerance decreased during constant clinching, with Parker slipping to the canvas several times during grappling.
The underdog ended stronger, but many rounds were challenging to assess. Nevertheless, former world champion the boxing analyst - working with Dazn - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
The victor progresses, but with the likes of heavy hitter Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - based on this performance - still appears challenging.
Hatton Homage Motivates Local Rivalry Contest
In the secondary fight, Lyndon Arthur beat Rea by split-decision in a outstanding all-Manchester fight to win the European light heavyweight championship.
The stadium became quiet for a extremely emotional tribute ahead of the contest as 10 bells tolled in remembrance of local hero Ricky Hatton, who died at age 46 in last month.
It was the first major televised boxing event in the urban center since the passing of Hatton. As the final chime ended, the quiet became a shout of "there's only one Hatton".
The competition within the ring equaled the sentiment. The eventual winner was floored by a powerful punch squarely on the chin in the initial stage, standing uncertainly to his position on the eight count.
But the traditional red shorts of Arthur soon came forward again. Across the ring, the opponent - in opposing blue - was damaged soon, significant bruising developing under his face as the duo exchanged hard punches.
The challenger, 27, landed power punches but Arthur, 34, responded in kind with stinging uppercuts as the pace hardly diminished over the full distance.
Arthur narrowly won the verdict with official scores of draw, narrow lead and wider gap, but the two athletes were relentless and full of heart, exactly what their inspiration Hatton stood for.
