The former White Hart Lane captain has praised the 20-year-old central defender for his performances this season, and says the starlet will gain confidence from the experience
The 20-year-old has impressed at the heart of Andre Villas-Boas' back line this season, keeping experienced players such as Michael Dawson out of the side, and scored a header in Spurs' 2-1 defeat to Manchester City on Sunday.
After Roy Hodgson rewarded the central defender with a squad place for the friendly on Wednesday, former club defender King believes Caulker's confidence will sky-rocket after receiving such an honour.
"[Caulker's] been fantastic, he's slipped into the team seamlessly and is so composed for one so young," he told Spurs' official website.
"Quite rightly, his form has been recognised and it's brilliant for him that he's been called into the England squad. "
Caulker played 45 minutes in the first five Premier League games of the season, but has played every minute of the last six and King feels the youngster can only benefit from being called up to international duty at a young age, highlighting his own experiences as evidence of how it can shape a player.
He continued: "Having been there myself, it's a big confidence-booster when you first go into the England squad.
"You come back to your club with your head held high, so confident, really believing you are a player. I remember it was a brilliant feeling for me and it will be beneficial as well for Tottenham he he goes on to win that first cap."
King made 21 appearances for the England national side in a career dogged by injury, after receiving his first cap against Italy in 2002.