The 22-year old midfielder, currently plying his trade in the Victorian Premier League with the Oakleigh Cannons, is set to be rewarded with a Heart contract when the VPL season finishes.
A former Melbourne Knights junior, Kalmar came on in the second half of the Heart's pre-season friendly with English Premier League club Everton last Wednesday and performed admirably in the defensive midfield position which had earlier been occupied by ex-Socceroo Josip Skoko.
Kalmar admitted it was a buzz to be out on the pitch with such big names like Tim Cahill and Louis Saha and said he was looking forward to the upcoming A-League season with a brand new franchise.
"It was fantastic to be a part of it," he said. "To see these guys on TV and to actually be running around with them is just amazing. It was good to see all the supporters come out in our first real big game.
"This is my first professional contract. I can't get the smile off my face, to be honest."
Kalmar added that the current Heart squad members were proving to be a very positive influence on his game as he strives to make a first-term appearance in his first season.
"They're fantastic, always asking how I'm going and helping me through," Kalmar added. "The younger and middle-aged guys really look up to them.
"It's slowly starting to jell and we're all getting to know one another.
"My goals for this season would be just to get a run first and progress from there.
"I'm just taking everything as it comes and enjoying the experience."