Welcome to the board! Consider picking up a guy like Michael Morse - someone with dual elgibility who can help you at two positions so you won't run into this type of situation.
With two waiver moves left however, I'd only advise making a move if you can play the person you're going to pickup. If you have the roster spots filled already, no point in picking up someone to play once a week.
Hope this helps.
Keeper League:
F) N.Backstrom, E.Malkin, V.Lecavalier, P.Mueller, A.Mcdonald, B.Boyes, A.Hemsky, S.Horcoff, K.Turris, D.Jeffrey, M.Perreault, C.O'Reilly, S.Upshall, M.Erat, S.Gagne, D.Legwand D) S.Souray, M.Streit, A.Babchuk, T.Gilbert, I.Cole, J.Hillen, M.Methot G) B.Elliott, S.Varlamov, C.Ward, J.Reimer P) N.Kadri, E.Kuznetsov, S.Shirokov, V.Tarasenko, J.Blum, OEL, J.Moore, O.Pavelec