Severin and Kiernan could come into the reckoning for the Scottish Premier League clash with Celtic at Rugby Park.
The duo's arrival is a boost for Killie's survival hopes. "We've not got such a big squad and we've got four or five big players out," Calderwood said: "I think this is our sixth game in 18 days."
Killie have lost their last 25 meetings with Celtic in all competitions and Calderwood's predecessor, Jim Jefferies, never managed to beat them in his near eight years at Rugby Park.
But the new manager has tasted success more than once against the Hoops, famously knocking them out of the Scottish Cup two years ago while in charge of Aberdeen.
Asked if his personal successes might make a difference tomorrow, Calderwood said: "I hope so.
"We're under no illusions over how difficult it is, but it's about self-belief.
"You've got to get the breaks on the day and hopefully Celtic don't show the form that we know they can produce."
Killie fought back from 3-1 down to draw 4-4 with Dundee United on Saturday and Calderwood added: "We did really well against a good Dundee United team.
"It's not often that you go behind against Dundee United and can pull it back, because defensively they're normally so, so strong.
"We'll take a lot of heart from that."
Calderwood admitted he had not personally watched Celtic live this season but was not sure it would have done much good anyway, considering the number of comings and goings there have been under Tony Mowbray this month.
"Tony's changed it around a lot so it'll be interesting," he said.
"But you know how Celtic are. They've been trying to play the same way for years and years.
"They always try to play football and that's the way Tony is.
"The pressure's always on the Old Firm; we've got nothing to lose, and hopefully we can give it a good go.
"It's a long time since Kilmarnock beat Celtic."
Calderwood hopes Rugby Park plays its part tomorrow night.
"It's always a wonderful atmosphere at the old stadium," he said.
"Celtic always bring a big support."
And despite many of his players beginning to tire after such a hectic recent schedule, Calderwood said: "These are the games you want to be involved in as a player and you don't really feel the tiredness at that moment in time."