Given Sandstrom's injury history, Ustimenko coming back off hip surgery, I'm sure they have a veteran scrub for depth somewhere.
None of these prospects are ready this year, Fedotov is under contract, Kolosov is a 19 year old we drafted in the 3rd rd (and so far, looks like a huge steal), Sandstrom is 24 but injuries have really slowed his development (over the last six years, 93 SHL games and 13 AHL games, he just doesn't have much pro level experience), Ersson (22 in Oct) has 82 SHL games under his belt.
This year will give a better read on these four and their NHL readiness, if Fedotov and Kolosov finish in the top ten in the KHL in S% they are prime candidates, if Sandstrom and Ersson shine in the AHL, same.