UK light heavyweight Joshua Buatsi secured a victory yet disappointing beginning to life under recent management with a points victory over Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a judges' verdict in a competitive ten-round bout at the Co-op Live Arena.
But Parker had his moments, delivering effective clean blows in a match where the styles never quite clicked, with frequent clinching marring the contest.
The officials had it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my best performance but what do champions do? They win," the victor commented in the ring as he was faced disapproval from the spectators.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in last winter - to claim a 20th career victory.
Some ringside observers believed the challenger, thirty-one, merited the win but the contender suffered the second setback of his 28-bout career.
The Champion Claims Victory in Slow Match
The fighter's advancement has plateaued in recent times through promotional disputes and extended periods of lack of fights.
Previously predicted as the future of the British fight scene, he now is positioned trying to realize his potential - perhaps in what feels like a last chance - under fresh management.
He began cautiously, with both competitors prepared to take risks in a cagey early stages.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was participating in his second appearance at the higher weight class.
By the halfway stage, Parker had made it competitive, causing problems for Buatsi, who worked behind a solid defense to narrowly win the more effective rounds.
The spectators' acceptance diminished amid constant clinching, with Parker going down multiple occasions during close exchanges.
Parker ended stronger, but several stanzas were difficult to score. Nevertheless, ex-champion the boxing analyst - providing analysis for Dazn - had it strongly leaning for Parker, giving Buatsi just only one stanza.
Buatsi moves on, but with the caliber of power puncher Benavidez, and Eastern European fighter Bivol ruling the division, the road to world glory - judging by this showing - still looks steep.
Hatton Tribute Inspires Manchester Derby Fight
In the secondary fight, Lyndon Arthur beat Rea by close verdict in a excellent local rivalry contest to capture the European light-heavyweight championship.
The venue became quiet for a extremely emotional homage prior to the bout as a bell ceremony tolled in memory of local hero Hatton, who died aged 46 in recently.
It was the premier televised fight night in the urban center since Hatton's death. As the final chime faded, the stillness transitioned to a roar of "there's only one Ricky Hatton".
The competition during the bout matched the emotion. The eventual winner was sent to the canvas by a significant blow directly to the jaw in the initial stage, rising shakily to his footing on the referee's count.
But the red-colored equipment of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was marked up quickly, noticeable damage appearing under his orbital area as the pair traded hard punches.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, fought fire with fire with powerful upward punches as the action rarely dropped over the full distance.
Arthur barely secured the verdict with official scores of draw, narrow lead and wider gap, but each competitor were determined and full of heart, all the qualities their inspiration the legend stood for.
