British light-heavyweight Joshua Buatsi earned a win yet underwhelming beginning to life under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a majority decision in a tight ten-round fight at the boxing arena.
But Parker found success, connecting with powerful clean blows in a fight where the styles never quite clicked, with constant grabbing spoiling the contest.
The scoring judges scored it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my best showing but what do champions do? They succeed," the victor commented in the ring as he was met by negative reactions from the spectators.
The Londoner bounced back after his first professional defeat - an thrilling contest with his previous opponent in February - to secure a 20th pro success.
Some ringside observers believed the challenger, thirty-one, deserved the decision but the Derbyshire fighter endured the second defeat of his 28-fight professional journey.
Buatsi Secures Victory in Uneventful Match
The fighter's advancement has stalled in recent years through promotional disputes and considerable time of inactivity.
Earlier forecast as the next star of UK boxing, he now finds himself trying to realize his potential - perhaps in what feels like a last chance - under new promotional backing.
He started carefully, with the two boxers ready to overcommit in a cagey opening few rounds.
Parker, whose only previous defeat came at the lower weight class against John Ryder in two years ago after breaking his hand in the contest, was making just his second appearance at the higher weight class.
By the halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who worked behind a solid defense to edge the cleaner periods.
The spectators' acceptance decreased during frequent holding, with the challenger falling to the floor several times during grappling.
The underdog closed well, but several stanzas were difficult to score. Although, ex-champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
Buatsi moves on, but with the caliber of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still seems difficult.
Ricky Hatton Tribute Fuels All-Manchester Fight
In the supporting bout, Lyndon Arthur defeated Bradley Rea by close verdict in a outstanding all-Manchester contest to capture the continental championship.
The venue fell silent for a profoundly moving tribute before the fight as a bell ceremony sounded in honor of Manchester's own Hatton, who died 46 years old in recently.
It was the premier televised match card in the location since Hatton's death. As the last bell faded, the stillness became a shout of "only one Hatton".
The fighting during the bout equaled the emotion. Arthur was floored by a left hook squarely on the jaw in the initial stage, standing uncertainly to his position on the referee's count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. On the opposite side, Rea - in competitive blue - was injured early, noticeable damage developing under his face as the duo traded hard punches.
The challenger, 27, connected with strong blows but the champion, 34, matched the intensity with stinging uppercuts as the action rarely dropped over twelve rounds.
The victor narrowly won the decision with judges scorecards of 114-114, close margin and clearer margin, but each competitor were persistent and brave, all the qualities their idol Hatton represented.
