The 28-year-old was included in manager Fabio Capello's provisional 30-man squad, but his bid for a seat on the plane to South Africa suffered a blow on Monday night when he remained on the bench for the Wembley friendly against Mexico.
Warnock, who was also an unused substitute in England's previous friendly win over Egypt last month, is likely to miss out on a spot in Capello's final party to Leighton Baines, who played at left-back on Monday.
But the Villa man is refusing to abandon hope just yet, and is counting on a run-out in Sunday's final warm-up match against Japan in Graz to prove his worth.
"You just need to try to get on the pitch to show what you can do but we'll just wait and see what happens at the weekend," Warnock told the Birmingham Mail.
"I've been training every day with everyone and been part of it, but it just wasn't to be the other night.
"I know it's going to be difficult. I think everyone's in with a shout and you've got to be optimistic. You just never know."
Warnock revealed Italian boss Capello is staying tight-lipped about his final line-up, and insists he is grateful just to be involved.
"What's the manager said to me?" added Warnock. "He hasn't said anything.
"I think you just know you're in his plans, you're in the 30 and it's good to be involved. I probably wasn't expecting to be in the 30 if I'm looking at it from the last game.
The defender admits it will be tough competing with Baines for a place in the party, particularly since the Everton man is more established in the England set-up.
"With Bainesy playing against Egypt I thought it would be difficult to get in the squad," he added.
"Yes, it is frustrating, but you know it's going to be tough to play and get a part
in the game. I knew it was going to be difficult because Bainesy's done well but that's all part and parcel of it."