Murray, who was not in the matchday squad for Portadown’s most recent Bluefin Sport Championship game against Larne, returned for a second spell at Portadown in May having worked with Matthew Tipton at Warrenpoint Town.
“Darren has been unable to commit fully to the demands that we ask of all of our players,” said Tipton in a brief Portadown club statement. “It is vital for the players to buy into our work ethics on and off the field for us to build a platform that enables us to move forward.”
Tipton signed the striker at Shamrock Park following his release from Crusaders after failing to report for a fixture.
The prolific striker originally left Portadown by forcing a move to Cliftonville with a submitted transfer request.
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In an exclusive Johnston Press interview following that May return to Portadown, Murray said: “I’m just trying to get back on track, enjoy my football and score goals.
“I just want people to judge me for what I do on the football pitch.”
Murray was unavailable for comment following the release of Portadown’s statement.