Broker finnCap says that shares in JD Sports remain cheap at a discount to the retail sector, and the stock is worth a 'buy' following a great trading update that beat expectations.The sport-themed fashion chain reported Friday that like-for-like sales over the 5-week Christmas period were up 2.5% and cumulative LFL sales for the 48 weeks to 1 January increased by 3.1%.With the group expecting to exceed pre-tax profit expectations for the year, finnCap raises its forecasts for 2011 by 5.4%.However, analyst David Stoddart says that "headwinds in 2011" have restricted the positive base effect on 2012 forecasts, and ups its estimates for next year by a lesser 2.7%.The target price is placed at 1,125p.