 At the age of 14 in 1904, Kilner reached the Mitchell Main first team. Although selected regularly from 1905, Kilner was not particularly successful with the bat. He displayed aggression but often attempted difficult shots and consequently lost his wicket. His bowling was more effective but used infrequently. By 1909 his batting improved; he scored his first century for the team and began to make consistently good scores, attracting the attention of Yorkshire.
