I suppose it could be possible in 10 minutes but you'd be out of breath!
Ten minutes easy via the steps or British tip. It was less before the station moved!
Other Merthyr train trips I've seen us play at include Bath at Twerton, Hednesford, and the old Worcester City ground from Foregate St. Taunton is 10 as is Bristol Manor Farm at Sea Mills too. Some other grounds already mentioned like Kidderminster...10 minutes. Many more were a little further away like Yate, or a huge trek like Cheltenham or Gloucester let alone Salsbury or Tiverton!
Porth at Dinas Park is under 10 from Dinas Rhondda likewise Risca fc and whoever uses the Gwent academy at Ystrad Mynach.
Pontypridd Town in Ynysyngharad Park is ten minutes too but they've moved out.
Troedyrhiw FC at the Willows by the station but is now a rugby ground. There's plenty of rugby grounds near stations but that's anther thread!