UK light-heavyweight Joshua Buatsi made a winning yet underwhelming beginning to life under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a judges' verdict in a competitive ten-round contest at the Co-op Live Arena.
But Parker had his moments, connecting with powerful clean blows in a contest where the techniques failed to mesh, with constant grabbing marring the action.
Two judges had it 96-94 to the winner, with the third a even score.
"It wasn't my greatest display but what do champions do? They succeed," the victor stated in the ringside as he was faced boos from the audience.
The Londoner returned to winning ways after his initial pro loss - an epic battle with his previous opponent in last winter - to earn a 20th career victory.
Several boxing experts felt Parker, thirty-one, should have been awarded the victory but the Derbyshire fighter suffered the second setback of his 28-match career.
The Champion Secures Victory in Slow Match
His career development has stalled in the past few years through management issues and long spells of inactivity.
Once tipped as the next star of British boxing, he now is positioned trying to achieve expectations - perhaps in what feels like a last chance - under recent support.
He began cautiously, with the two boxers willing to overcommit in a tentative initial rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in 2022 after damaging his hand during the bout, was making just his second bout at the higher weight class.
By the fight's midpoint, the underdog had stayed in contention, causing problems for Buatsi, who utilized a protective stance to narrowly win the cleaner periods.
The audience's tolerance diminished amid regular grabbing, with the challenger slipping to the canvas multiple occasions during close exchanges.
The underdog finished the stronger, but many rounds were hard to judge. However, ex-champion the boxing analyst - working with the broadcast network - had it particularly wide for Parker, scoring for Buatsi just one round.
Buatsi moves on, but with the caliber of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Hatton Memorial Fuels All-Manchester Contest
In the co-main event, Arthur overcame Bradley Rea by close verdict in a excellent local rivalry contest to win the continental title.
The arena fell silent for a deeply poignant homage ahead of the contest as 10 bells sounded in memory of local hero Hatton, who passed away at age 46 in recently.
It was the initial significant broadcast fight night in the location since Hatton's passing. As the final chime disappeared, the silence gave way to a shout of "only one Hatton".
The fighting during the bout reflected the feeling. The eventual winner was floored by a powerful punch directly to the face in the initial stage, standing uncertainly to his position on the eight count.
But the red-colored equipment of Arthur soon pressed ahead again. From the other corner, Rea - in opposing blue - was marked up soon, heavy swelling forming under his orbital area as the duo landed powerful shots.
Rea, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the pace hardly diminished over twelve rounds.
The victor barely secured the result with scoring tallies of 114-114, 115-113 and clearer margin, but each competitor were determined and full of heart, all the qualities their idol Hatton embodied.
