The old Vetch Field ground would have been the football ground which was the farthest west of all the 92 club grounds in the English (and Welsh, in that two Welsh clubs are in it) league.Ninian Park, home to Cardiff City FC is the next most westerly
Portman Road, Ipswich, the home ground of Ipswich Town FC is, just, the most easterly of them. (Colchester's ground is west of it by a tiny margin of longitude)
138 hours is quite a long time in travelling. If the idea is to go from West to East that seems a great deal of time:Vetch Field to Portman Road is 275 miles, a rate for distance of 2 mph, a slow walking pace.
A visit to each of the 92 clubs in the League would take a lot longer on foot !It might be possible by train, coach or car in 138 hours but it would involve going as far as Plymouth Argyle in the South West, as far North West as, say, Liverpool, as far to the North East as somewhere like Sunderland and as far to the South East as Brighton and Hove plus visiting the myriad clubs in between.Still, if you could average 30 mph that would make about 4,000 miles, which should be enough.
The clubs referenced in your post are in the same division. A visit to all in that division would reduce the visits to 22 but could still involve some big journeys !
I'll go for it being an attempt at visiting all 92

15 is a strange number for soccer. The governing body now allows 5 substitutes of whom 3 can be used in play, so a team on the road would be 16.