The German-born player is eligible to represent Nigeria, and was initially sounded out by former coach Samson Siasia on a visit to Germany last year.
But Keshi says his attempts to re-establish contact has been met with a brick wall.
“I have called Sam over 15 times and each time the phone dovetails into voicemail. I have always left a message, but the player has not responded to any of my messages. That to me is shocking and says a lot about his readiness or otherwise to play for the Super Eagles.”
Keshi said he was informed by some Nigerians based in Germany that the player may have refrained from calling or picking his calls because he does not speak the English language.
“That also does not jell with me, because there are several Nigerians who speak the German language fluently and if he writes in his native language we can easily infer whether he wants to play for us or not.”
But Keshi made it clear that while the door remains open for the player, he has decided to look beyond him at other prospects.
One such prospect is Atletico Beleares midfielder Raheem Lawal, who last turned out for Nigeria at the London 2012 Olympics qualifiers in Morocco, where Nigeria failed to make the cut for the games.
“Lawal is young and talented and many Nigerians who have watched him have said he will go places in future. Those are the type of talents that we are looking up to in raising a team that Nigeria will be proud of in the near future.”