And despite a couple of injury setbacks, the Czech international says he is a lot happier down the road from his parent club than Teesside - and not because of the 200 miles difference.
At Boro, Kalas flitted back and forth between right-back and centre back, and as a result, thinks he was never able to play to his true potential.
He got 35 starts under Aitor Karanka between January 2015 and April 2016. At Fulham he has been on the starting sheet 23 times already, and it would have been lot more except for a pair of hamstring injuries.
"I am playing where I like to play with Fulham, at centre back," he said.
"At Middlesbrough, I ouldn’t get used to either of these positions because they changed.
"But now I know what to expect and where I’m going to play.
"It doesn’t matter if it’s Rags (Ragnar Sigurdsson), Michael Madl or Tim Ream as a partner, we have made good relationships - but I know I like to play as a central defender."
Kalas an co plan to bounce back from a 1-0 defeat to Birmingham when they entertain struggling Wigan at Craven Cottage on Saturday.