Jay Bothroyd has returned to parent club QPR following the expiry of his loan spell at Sheffield Wednesday.
The 30-year-old teamed back up with Owls boss Dave Jones when he joined Wednesday in August and made 14 appearances for the Owls, scoring one goal.
Jones confirmed earlier this week that he would not be looking to extend Bothroyd's stay at Hillsborough, while QPR manager Harry Redknapp is keen to boost his firepower as he looks to mastermind the London club's Barclays Premier League survival.
Bothroyd, who spent over two years at Cardiff from 2008 while Jones was in charge of the club, has not featured for the Owls in their last seven matches and scored his solitary goal for them in the 1-1 home draw with Leeds in mid-October.
The midfielder sees his current deal expire on January 8 but manager Micky Adams has decided not to table fresh terms, leaving McAllister free to find another club.
"It's unfortunate that we weren't able to offer Sean more first-team opportunities but that underlines the competition for places we have among the squad," Adams told Vale's official website.
"He's a great professional and we wish him the very best of luck for the future."
McAllister joined Vale on a short-term contract at the start of November but has made just three appearances, two of those coming off the bench.
The 32-year-old was relieved of his duties just minutes after the club's 2-1 defeat at Bristol Rovers, bringing to an end his near four-year association with the Pilgrims.
And the former Crystal Palace midfielder will now take time to ponder his future and spend time with his family but having only hung up his boots 14 months ago, and still six months away from his 33rd birthday, he admits he is not ruling out a playing return.
"You never know - I might go back and play," he told the club's official website. "I've seen some players in teams in this division and others, and I sometimes think I still might be able to earn a living that way.
"I'll see how I feel, whether I want to retire. Sometimes you think 'is it worth the hassle?'
"All the stress, the late nights and the work. I don't know. I'll have a bit of down time. I've never really had down time at all since I was about 16. It's been football non-stop.
"I'll spend some time with the family and let everything settle down."
Fletcher was visibly emotional when he spoke to the press shortly after being told of the board's decision and he was quick to wish the Argyle players all the best for the rest of the season.
"It's a real good football club that has been through some real tough times. But hopefully it's going the right way - on and off the pitch," he said. "It's tough when you speak to the players; they've put a lot in and we've been through a lot together.
"There's some real good players in that changing room. Some real good characters. I wish them all the best. They've got some good quality and are still young. They've got a real chance in the future."
