In Test Cricket batsman’s role-play plays a huge role to build team’s total, particular if condition are suited for bowlers.
In the ongoing Ashes scoring runs has been very difficult for both teams. Hence staying at the crease becomes vital to build totals.
I believe Travis Head was dropped for same reason. Although he looked in form and most likely to score runs after Smith in this Australia squad. His role-play(staying at crease) dropped alarmingly after every match.
Below is match-wise stats table of his role-play.
In last 2 test there is a huge drop in his involvement in partnerships, and occupation of crease.
Mitch Marsh has replaced Head for the final test at The Oval. Marsh role-play would be of a bowling all-rounder.
Head omission might be harsh and barring Mathew Wade one cannot think of any other middle-order batsman who could have been left out. Both Wade and Head are multi-skill player and are asset to Australian team in all format.
Here is Wade role-play in this Ashes. It is very clear in last 2 Tests Wade had increased his role-play along with runs from his bat!.
I am sure it was not an easy decision for selectors to drop Head and keep Wade as they both are multi-skilled players.
Both have opened in limited overs cricket (v/s Pak Head involved in record opening stand of 284 runs with Warner)
Both occupied various batting position in both format
Both have kept wickets (Wade in both format and Head in ODIs)
Both decent(under used) part-time bowlers in both format.
All stats updated at end of 4th Ashes Test, Old Trafford 2019.
Link to role-play