You seem to forget how well Hernandez played in the game against Chelsea, which he started and showed none of the weaknesses you ascribe to him. Oh no, silly me, you did comment on that game even though you didn't actually see it, as it wasn't broadcast in the US. I guess you won't have seen the Newcastle cup game for the same reason. He started in the PL against Wigan - did you see that game - played 90 minutes and managed a goal and an assist.
It doesn't take a genius to work out that Hernandez may be subbed late in the game if he does start. Likely it would be because he'll have done his job and it will be time for fresh legs and/or to give someone else a run-out. Possibly, it would be because we're losing 2-0 and need someone else to come on and get the hat-trick!