The Irish star - like most of his team-mates - chose to look forward rather than dwell on Saturday's 3-0 third round win against Palace.
He said: "We know we haven't been playing as well as we're capable of and it was important we got the win and played some good football along the way.
"Now it's important we take this into the Premiership.
"We haven't been doing very well in the league. We've done well in the cups but we need to start getting a few results in the Premiership.
"Wednesday will be tough, Birmingham are a hard-working side but if we can play like we did against Palace I don't see any reason why we can't go out and win that game."
Robbie added that the players were more than aware of their current league position and the flak flying as a result.
"We have to be strong enough not to let it bother us," he insisted. "We've a strong set of lads and we'll be okay. We have good characters here. We're aware of our position but we won't let it affect us."
Robbie Keane says it's vital we take our FA Cup form into tomorrow's Premiership clash against Birmingham City.