Originally I had thought it was a simple case of the upper folding a bit too harshly and rubbing on the top of my foot.
However, the upper is really soft and smooth on the inside so this didn't quite seem a good fit for the cause so in the evening I had a good feel on the inside of the shoe for any seems or possible friction points. The culprit as a thin sheet of hard plastic used to reinforce the area of the upper where the laces go through the lace holes. These bits of plastic covered by a black material which in theory should protect the foot from coming into contact with the plastic.
I removed the laced, pushed the tongue back and bent the upper back to show the reinforcement with the black material that covers the hard plastic plastic. Both the hard plastic and material cover are stitched to the upper along one seam at the top next to the opening.
The plastic and black material are glued together but the two of them are not glued to the upper so can be bent back. Bending them back reveals the white plastic and culprit of my blister.
Except it's not just one blister, while only me left foot ended up bloodied, it turns out that my right foot has a blister in exactly the same place (top of the 4th toe) that hadn't burst and hadn't bothered me too much during the run.
Clearly this is a design or manufacturing fault with the shoe, personally it think it's more likely a design fault that for some perplexing reason didn't get spotted/corrected during development.
This issue leaves me with an interesting problem - I love the light weight, good balance of ground feel and protection, the sensible foot shaped last, low heel drop, the grip, the vast majority of the upper is just excellent, but... this blister problem while not a deal breaker yet isn't a good one to deal with on an expensive new shoe.
I'm not one adverse to shoe surgery, my super wide feet normally require some form of modification of shoes to accommodate them, so two solutions might be to:
- Trim the plastic area back so that it's not over my metatarsal heads and where my feet bend the most. Any trimming would have to make sure that plastic remains nicely curved with no new corners.
- Glue the plastic and black material cover directly to the upper to avoid any chance that the black material would ride up over the plastic.