The 20-year-old replaced the injured Terry to make his Premier League debut against Liverpool in the recent 2-0 win at Anfield, having spent the previous two seasons on loan at Vitesse Arnhem.
Kalas joined the Blues from Czech side Sigma Olomouc in 2010 for a fee reported to be in the region of £5.2million and has three first-team appearances to his name.
As a youngster, he modelled his game on Terry and admits he is delighted to be part of the same team as him.
"I always watched Chelsea and wanted to play for them. It was because JT was my idol," he told The Sun.
"What marked him out as my star player was how he read the game, his experience, his heading - everything.
"It was a dream from the moment I signed to be at the club for a long time like JT and become a legend. But I can't begin to compare myself to him yet."
Kalas tried to remain modest when asked if he was ready to replace Terry, who turns 34 this year, but says he is prepared to step in when required.
"If I say yes, I show myself to have a big head. If I say no, it's like I don't have confidence - it's somewhere in between. But confidence-wise, yes I think so," he said.
"If I wasn't confident to start or come off the bench, then I shouldn't be here."