Two evenly matched sides on underlying chance numbers, each with a thin midfield and a depleted squad. The table and recent away results favour the visitors, and the home side's defensive losses are in exactly the area the visitors attack.
Stoke are fourth and have won four of their last five away games, with a lot of their goals coming from corners and crosses. Portsmouth are tenth and have lost both of their usual centre-backs for weeks, which is the pairing that has to deal with that aerial delivery. Portsmouth are also missing both forwards, so their attack has to find goals without its usual outlets, even though they have kept scoring at home.
Stoke lose their suspended midfielder too, and their conceded chances are worse than their results suggest, so this is no walkover. The first goal decides the shape: a Stoke lead lets them sit and defend. That's why I'm siding with Stoke, with the draw returned if Portsmouth hold.
