Arsene Wenger left exposed by Alexis Sanchez sale to Manchester United

When Manchester United last bought a player from Arsenal, then manager Alex Ferguson complimented counterpart Arsene Wenger on the hard bargain he drove in selling striker Robin van Persie, saying the Frenchman "could run a poker school in Govan".

That reference to the raw end of Glasgow where Ferguson grew up suggested Wenger had extracted the maximum possible from a difficult situation in ensuring United paid the then hefty sum of 24 million pounds ($33.50 million) for the Dutch striker.

Five and a half years on and it is unlikely Wenger will receive any pats on the back for his part in Alexis Sanchez's exit from Arsenal, a move that all but confirms how far the London club have fallen behind the Premier League powerhouses.

While Van Persie departed a year before his contract expired after, like 29-year-old Sanchez, rejecting a new deal, the Chilean has followed the same road for a knockdown price six months before he could walk out of the club for nothing.

Theo Walcott, another mainstay of the Wenger years, joined Everton last week, Alex Oxlade-Chamberlain is starring for Liverpool after threatening to run down his contract last year, while Jack Wilshere and Mesut Ozil can leave The Emirates for nothing at the end of the season. Yet Wenger remains in place.

It is hard to remember a time when the 68-year-old Frenchman has appeared less revered or under greater pressure, although Saturday's thumping of Crystal Palace will at least support his argument that they have talent in the wings.

As the Sanchez saga rumbled on from last summer, when Arsenal reportedly rejected 60 million pounds for his services, Wenger has appeared progressively more uncomfortable in fielding the never-ending questions about the Chilean's future.

MOUNTING UNCERTAINTY

The uncertainty affected Arsenal on the field, with their former striker Thierry Henry highlighting the lack of enthusiasm from Sanchez's team mates to help him celebrate when he scored against Crystal Palace in last month's Boxing Day fixture.

For the first time in Wenger's 22 years at the club, the previously all-powerful Frenchman has appeared powerless to shape events, reduced to responding with platitudes at every mention of Sanchez's impending move to Manchester.

Now Arsenal's creative dynamo has gone, the arrival of United midfielder Henrikh Mkhitaryan as part of the deal is unlikely to silence the calls for Wenger's own departure. Last May, when Arsenal won the FA Cup, Wenger signed a new two-year contract and talked confidently of mounting a Premier League challenge this season.

Arsenal Chief Executive Ivan Gazidis said the aim was "to compete for and win trophies here and in Europe", but it is unlikely he had in mind the League Cup in which Arsenal are in the semi-finals having drawn the first leg at Chelsea.

If anything, winning that trophy might only serve to highlight their decline since Wenger secured the last of his three league titles back in 2004. In a very real sense, the sale of Sanchez may mark the end of an era.