If the former Coventry, Norwich and Oldham midfielder really had transferred from the poachers to the gamekeepers, it would be a defection in the Eric Cantona or Sol Campbell class. In fact, McGuire is spearheading a major change in the way players are represented in their contractual negotiations, and indeed in their career development in both the sporting and commercial sense.
After years of handling such matters as a self-styled "trouble-shooter" - someone to whom players tended to turn when they felt unfairly exploited by their agent or club - McGuire decided last year that the PFA needed to set up its own agency. Business is booming, so much so that Phil Sproson, the former Port Vale defender, was recruited to work alongside him this summer. Another appointment is likely in the near future.
If the duo merely duplicated the work of agents, there would be little point in their Manchester-based operation. But this is not, they argue, a case of "if you can't beat 'em, join 'em". The PFA has business partners in areas such as tax, investment and property. More pertinently, especially where working-class teenagers are breaking into the Premiership world of substantial wages and instant fame, it offers what McGuire terms an "ethical dimension".
"I'm salaried, so I'm not earning off the back of any player and can give objective advice," says the 53-year-old Lancastrian who was in the same Coventry youth team as David Icke. "We provide protection, guidance and help with the media, so they can concentrate on their football.
"There are charges, because there are costs in running any service. But they are lower than any agent's, and the money goes into the benevolent fund for ex-players who are struggling financially."
McGuire has been negotiating contracts, from Iain Dowie to Joe Cole and Jermain Defoe, for 18 years. "When I started, there were only three or four agents out there," he says. "Some used to seduce players by giving them boots or sportswear. Over time, though, every man jack and his dog became an agent - any industry with a massive cash-flow attracts entrepreneurs, and football has been awash with money for 10 years."
His problem is not with agents per se. "Some do a good job. My beef is with the bad practice so many agents follow. It has been a free-for-all. Guys can come in from all areas of industry and set up as agents. It's ludicrous. They may learn about watertight contracts along the way, but in the meantime we often have to pick up the pieces.
"Their charges are often ridiculously exorbitant, too. They take from both ends: player and club. If they're greedy and want more, they go back to the player and say, 'I thought I was getting X amount from the club but I haven't, so you'll have to top me up'. Too often they don't top-and-tail agreements. By that I mean the wording is so loose that when the player comes to receive his money, guess what, it's not what it should be.
"That has happened because the regulations aren't tight enough. We have been on a working party with the Football Association, putting very tight rules together. The only problem is whether they will be enforced."
McGuire, who does not hide his "frustration" with the FA, doubted they would. "I was getting loads of players ringing, saying, 'This is the deal I've got from my agent. Is it a good one?' My reaction was, 'Ask your agent. He's the one getting paid'. We began to think, 'Enough is enough. We've got the experience and the expertise. Let's do it ourselves'."
The catalyst for the creation of the PFA agency was James Milner. He consulted McGuire when he first made the Leeds United squad. A week later, he danced past Chelsea's Marcel Desailly before curling in a stunning goal and McGuire realised it was the fresh-faced 16-year-old he had just met. When Leeds sought to tie their prodigy to a new deal, Milner called McGuire, who also acted for him in his subsequent moves to Newcastle and Aston Villa.
"As well as the contractual side, we've raised James' commercial profile. We've got him a car, plus a boot deal, but we've been careful to do things in an appropriate manner, with the right kind of articles and public appearances. We're exploiting his name, but for his benefit, and in a measured way that doesn't impinge upon his football. He has provided the template for the players we're now handling."
The client list includes Marlon Harewood, who has set the Premiership alight with his goals for West Ham; Curtis Davies, the defender that Bryan Robson, the West Bromwich Albion manager, likens to Paul McGrath and Des Walker; Lee McCulloch, who scored in Wigan's win over Bolton on Sunday; Neil Mellor, the young Liverpool striker; and Marc Bircham, Queen's Park Rangers' spiky midfielder.
Some agents dismiss the PFA set-up as "too soft", admits McGuire, claiming they are "too well in with the clubs". Yet there is a difference, he adds, between having a rapport (often stemming from the union bailing out clubs that cannot pay wages) and being in awe. "We have the clubs' grudging respect, but they know that we'll take them on. They see us as straight-talking, arsey and always standing our ground. But there's also a perception that we're not sexy enough. Well a lot of players are sick of the sexy agent because he's not even there when they're in contract talks; he's doing it from a phone in the office."
Sproson's background was with B Sports, an agency run by a Stoke-on-Trent lawyer - "a good grounding with an ethical company". But his recent experience with Davies' transfer from Luton Town suggests that time-honoured trade union tactics still have their uses. "The transfer window shut at midnight," he recalls, "and me, my PFA colleague Bobby Barnes [once of West Ham] and Curtis were at West Brom at 5pm. But we felt the deal was wrong. Albion were paying £3m, yet the money on offer to Curtis was little better than he was on at Luton. At one point we left Nigel Pearson [assistant manager] and the chairman [Jeremy Peace] alone with the player and his father. We said, 'If you can persuade him this is right for him over the next four years, we'll walk away'.
"Curtis was desperate to play in the Premiership. But they couldn't agree. We walked out. Bobby and Curtis drove south and I headed north. At 10pm we got the call to turn round and ended up negotiating a good compromise. It's about knowing how far to go without breaking the straw. The deal was done with five minutes to spare and his registration came through by fax at 11.58."
McGuire sees Davies, 20, as typical of the new breed of young player engaging the union as their agents. "Parents want their lads to be represented by us. There's a 15-year-old on Leeds' books who is tipped for a fantastic future, a midfielder called Danny Rose, and his family want us to act for him when he's old enough to be a member.
"We've taken on 20 players in four months and we've got people in all divisions. We're honest with them; those in the lower leagues understand there are limits to what we can do for them as agents. It works the other way, too. Marlon Harewood realises that he can progress commercially and contractually only if he keeps delivering on the pitch."
This overdue sense of perspective is filtering through to the clubs, according to McGuire. "Some are still paying too much to agents, and that's up to them. But the transfer window has helped bring stability and driven out some of the peripheral agents because there's not enough work. That still leaves 200 agents fighting for the work there is."
McGuire stresses that the PFA will continue to strive for all members, regardless of whether they commit to the agency. That said, he is convinced it will keep growing. "We're not about grabbing anybody and everybody," he says, "and in numbers terms, we're not in the top three. But within two years - no, 18 months - we will be."