Fernando may be referred to as a 'defensive midfielder' but he is as effective as a referee in terms of defending. Always there or thereabouts but rarely having an impact defensively. Nasri would do no worse in that position.
I am looking forward to Delph returning as I expect him to be far more effective both defensively and offensively.
I don't think it would be a stretch to say our best CL performances to date have been with Fernandinho and Fernando in midfield.