This week we continue our "quick" look at the Ruy Lopez, now starring lines with 5.d3 and 6.d3. It's a surprisingly poisonous approach for White, one that has been successfully used all the way up the food chain to Magnus Carlsen. It can be used as a geniune weapon, and it's not at all clear that Black has some way of achieving a foolproof equality. (I'm not claiming that White has a certain edge, either, only that it's still a live option for White.)
Additionally, it's practical for White, in two ways. First, it's comparatively easy to learn and understand, and it's not necessary to know all that much theory to do a reasonable job with it. Second - and this may be its biggest selling point - it cuts out the Marshall Gambit, the main lines of the closed, and even the Open if you play d3 on move 5. Objectively, I suspect that the main lines, when well-understood, give White his best chance of proving an edge. As an interim measure, however, and also for a bit of variety I think the d3-systems are worth trying from time to time - especially those who don't want to spend the time learning the rich but extensive theory of the Ruy's main lines.
So you might have a look at my ChessVideos show this week, where I cover these d3 lines and present Carlsen's smashing win over Veselin Topalov from the Nanjing tournament that took place exactly a year ago come Tuesday. As always, the show is free (one-time free registration is required) and will be available on-demand for the next month or so.