Calderwood left Kilmarnock at the end of the season, saying he was unhappy about the playing budget and the prospect of losing coach Sandy Clark to cut costs at the debt-struck club.
"I'm unhappy with the way I'm playing, I couldn't play the way I wanted to, " added the Swiss, who needed five sets to overcome Alejandro Fall in the first round and four to oust Ilija Bozoljac in the second.