If we could easily replace these players, then we'd be Arsenal, ManU, Chelsea, or the [Poor language removed] with the money they spend.
But since we don't have that money to spend, Moyes has had to mold and craft a squad that plays well as a team and as a unit without all of the flair that a team like Arsenal has.
That invariably means that we'll have one or two players who undoubtedly would be considered "weak links" but by no means kill us everytime they're on the field. They're just solid professionals.
Now before you get on me about upgrading those areas, consider what this team looked like under Walter Smith. We were a whole team full of weak links and our play and standing in the table illustrated that.
But Moyes has slowly built the squad up over time and solidified several positions in the pitch that we won't have to worry about for a good while. In the meantime, he will continue to try and upgrade where possible while maintaining a good team chemistry and doing so within the budget he has to work with.
I know that many think that certain players will never be dropped but my guess is that if Moyes feels he needs to make a change for the better of the team, then he'll do so. I'm confident that going into the summer, Moyes knows what he needs to upgrade the team and probably has a few targets already identified.
IMWT.