Armitage made a scintillating start to his international career and was unfortunate to miss out on selection for the 2009 Lions tour before losing his way.
The London Irish full-back, bereft of form and confidence, was eventually replaced in the England team by Foden at the end of the 2010 Six Nations.
Foden has started every Test since while Armitage has travelled a rocky road, including high-profile suspensions last season for abusing an anti-doping official and for punching Northampton fly-half Stephen Myler.
But Foden scoffed at suggestions he is a certain starter for England in their World Cup opener against Argentina on September 10 in Dunedin.
The England management kept faith with Armitage through the dark times - he was invited to train with the squad while banned - and Foden has begun to see the old spark return.
Armitage is now in line to make his first Test start in 17 months in Saturday's Investec challenge against Wales at Twickenham.
"Delon and I have been competing for that 15 shirt over the last two years and he is looking sharp. I know he is breathing down my neck," said Foden.
"Delon has taken a lot of stick over the last couple of years but when he was starting for England back in 2009 he was one of the standout players every time he took the field.
"I am pretty sure we will see that Delon Armitage again. He is a great player, very talented.
"He is always pushing. He will get his chance in these (warm-up) games.
"It is good for me and good for him that we are on top of our games.
"You have to relish that challenge. If anyone shies away from that challenge you wouldn't be involved in the squad because competition is so high. That is a credit to the mentality we have."
Foden began his career as a scrum-half before moving to full-back but he is under consideration as a potential World Cup back-up to Ben Youngs and Danny Care.
England would be expected to take three specialist scrum-halves, but in Foden and Riki Flutey they boast versatile players who have played in the position before.
If Martin Johnson and the England management opt for only two specialists, they open up a place for an extra back such as the impressive Leicester centre Manu Tuilagi.
"Brian Smith (England backs coach) has been calling me aside and we have been doing a little bit. Riki has been doing the same," said Foden.
"I made a cameo against Ireland for 10 minutes (when Youngs was in the sin-bin). The good things is there is so much versatility in the squad."
Johnson yesterday cut his squad down to 40, releasing Joe Worsley, George Chuter, Thomas Waldrom, David Strettle and James Simpson-Daniel.
Among those retained in the 40 were Tuilagi and Gloucester wing Charlie Sharples, who was a late call-up into the original squad but has impressed everyone.
"I have been very impressed with them both. Manu is one hell of a specimin," said Foden.
"He weighs over 100kg, he runs like the wind and he has also got wicked feet. We did a fitness test today and he dusted me up in that. He is a fit guy.
"We saw the impact he had on the Premireship last year and he can make the same impact at international level.
"Charlie Sharples is the fastest white guy I have ever seen. We have done some speed tests and Charlie has been putting up some phenomenal scores and he has got a really good work ethos."
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