 He then moved even further south, joining London side Woolwich Arsenal in May 1908.Initially a reserve player, McKinnon made his debut on 12 December 1908 in a 4-1 defeat at the hands of Bradford City, and only made one more appearance in the 1908-09 season.He mainly played at left half, as an understudy to fellow Scot Roddy McEachrane, and it wasn't until 1911 did McKinnon supplant his countryman and become a regular in the Woolwich Arsenal side.