'Tis indeed true, but according to the Benitez mantra ("Possibilities, Possibilities, Possibilities"), Riise may have been a better bet to stay on the field at that time, as he would offer more of an attacking threat.
As for Warnock, I would love for him to be a great left-back - however recent performances have indicated that he apparently isn't, something that I have (like the original poster) been thinking for some time...
To look on the bright side, Finnan and Carra had great games, and Momo was looking solid and yet strangely composed in the first half - all bodes well...