If the diagnosis is correct, which isn't always clear, an epidural won't treat lumbar facet joints, because they are outside the epidural space. An epidural would be used for a disk problem but results are variable from patient to patient.
If it is facet joint sprain the treatment would be injection of both L4, L5 level, facet joints with corticosteroids and numbing medication. Results are variable and often dependent upon the precision in which the injection is placed. It can give almost total relief or no relief; and that relief is generally short term.
Back problems are difficult in a football player, but facet joint sprain is usually an easier problem to resolve than a disk problem.