DeCastro has been ruled out of his side's clash with the New England Patriots, leaving his spot at right guard open for Whimper to fill to protect quarterback Ben Roethlisberger.
"They haven't told me that yet," Whimper told the club's official website. "I'm taking the approach like I am. I'm a whole lot more confident playing guard this week.
"If they need me there I'll be ready. I'm willing and more than capable of coming in and helping this lineout."
The Steelers are 2-5 in their season going into week nine.