Former San Francisco 49ers receiver A.J. Jenkins could compete with former St. Louis Rams receiver Donnie Avery for a starting spot in the Kansas City Chiefs' offense.That coincidence illustrates the high level of turnover at the position around here.The San Francisco 49ers' Michael Crabtree and the Seattle Seahawks' Percy Harvin suffered serious injuries this offseason. The St. Louis Rams decided against retaining 2012 starters Danny Amendola and Brandon Gibson.