Don't you feel the nervousness could have come due to Martinez's style which we had become accustomed to for 2 years. That was not going to change in 1 season was it? Same way in Bobby's 1st season we saw a solid Moyes like defence.
About the intelligence factor, that is what you have DMs for. Schniderlin and Gana's stats for interceptions were very good last year. When you intercept passes, you start your own move forwards there and then. Now compare that to this season, those two are playing shambles and hence we are struggling. Every good team gets confidence knowing the defence is strong. We not only have a weak defence thanks to injuries and not investing there or not getting players across the line but ohr attack is weaker too. Some of it is due to Koeman I agree but there are other factors like Walsh and the board as well which people ignore.