Crystal Palace full-back Clyne made his under-21 bow in Thursday night's 5-0 thrashing of Iceland, which maintained England's 100% start to their European Championship qualifying campaign. The 20-year-old was then at Wembley on Saturday for the senior side's shock 1-0 win over Spain, which saw Rodwell and Walker both come off the bench.
The duo were part of the squad for this summer's Under-21 Championships in Denmark and Clyne told www.thefa.com: "As long as you are good enough, it doesn't matter how old you are."
He added: "If you are called upon, you are obviously good enough. It's good to see that young lads are getting in to the first team and that, if you take your chances, you can get in there."
Clyne admitted his own debut for the under-21s came as a shock. The right-back was drafted in on the opposite flank following injuries to Nathan Baker and Joe Bennett.
"I didn't really expect to start but, due to injuries, I got myself in there," he said.
"I worked hard in training to try and get myself into the team and I grabbed it with both hands. Hopefully, I have done enough to secure a place for the next game.
"I can do a job at left-back but I am predominantly a right-back. It's always good to have another position under your belt and, if called upon, I can always do a job at left-back, no problem."
He added: "Being called into the under-21s is a big deal for me, because it is a high level. I want to see and I want to know if I am up for, and capable of matching the standards of the under-21s. I want to see how far I have come.
"I always want to play for England and, whenever you put on that shirt, you want to give 100% and every time you train you want to do well for your country. Whenever I am called up, I will come and do my best."