Siddle bowled 16 overs, including 10 maidens, and conceded only 14 runs in England's second innings after not making the team for the first four tests of the series.
"I've been carrying a few drinks which has been disappointing, I would have liked my chance, but I didn't bowl as well as I could in the tour matches," Siddle told Sky Sports.
"I've been feeling good. Pressure is key -- that's what I've been able to build for the team. My plan was to get it going across Alastair Cook and it was a good battle."
England, who have already won the series, followed on 332 runs behind and reached 203 for six at the close, still 129 runs short of making Australia bat again.
"The follow-on is always hard, it was a long day today, but Pup (captain Michael Clarke) asked us what we wanted to do and he wanted to have a real go at winning this test match," Siddle, 30, said.
England wicketkeeper Jos Buttler, unbeaten on 33 at the close, admitted his team were in a bad position.
"We're up against it but we've just got to keep fighting and hang in there," he said.
He praised the example of England captain Alastair Cook who batted more than five hours for his 85.
"The captain showed that for most of the day," Buttler said.
"Everyone's very disappointed to come here and play as we have. I've had a tough series, it's been tough mentally when you keep finding ways of getting out, but you've got to keep scrapping."
Buttler was still hopeful of salvaging a draw with rain forecast over the next two days.
"It would be great if we could get out of this and a bit of rain would be great," he said.
(Writing by Ed Osmond; Editing by Ken Ferris)
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