This is something I said some months ago. Perhaps it would explain why I think this is a good move.
When we were going through a two month bad spell in the league, who did we have to change things ? Silva had practically half a squad to use considering how many weren't good enough or on loan at the time granted the loaners wouldn't have made a huge difference but it limited Silva all the same . Drop certain players and there was no adequate back up.
So more players who are available the better we can perform. Fresh legs, new ideas to the team, be a little less predictable to plan against?
Delph isn't going to win us the league single handedly sure, but a back up option for gueye gomes and whoever else we play in the middle, what's not to like for 8 million?
He won't play every week but then for us to have a good season, not everyone will. And most importantly , another point I've raised in the past, options. If a player is out of form, we have options rather than having to hope they come into form again.