Michalik's short-term contract expires this week and he is set for a move abroad.
Mustapha Dumbuya, Jon Harley, Brian Howard and Lee Williamson are also moving on at the end of their contracts, leaving caretaker manager Guy Whittingham looking for reinforcements.
"Lubo's said that he's going to find pastures new and head off abroad to play his football," Whittingham told Pompey's website.
"We had a meeting in the changing room after (Saturday's) game had been called off to thank all the players who are leaving for what they've done for this club. It certainly hasn't been easy.
"There are a few spaces available in our squad and we need to make sure we bring in the right people."